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f(n) = O(g(n))<br />

f(n) = Ω(g(n))<br />

Definitions<br />

iff ∃ positive c, n 0 such that<br />

0 ≤ f(n) ≤ cg(n) ∀n ≥ n 0 .<br />

iff ∃ positive c, n 0 such that<br />

f(n) ≥ cg(n) ≥ 0 ∀n ≥ n 0 .<br />

f(n) = Θ(g(n)) iff f(n) = O(g(n)) and<br />

f(n) = Ω(g(n)).<br />

f(n) = o(g(n)) iff lim n→∞ f(n)/g(n) = 0.<br />

lim a n = a iff ∀ϵ > 0, ∃n 0 such that<br />

n→∞<br />

|a n − a| < ϵ, ∀n ≥ n 0 .<br />

sup S least b ∈ R such that b ≥ s,<br />

∀s ∈ S.<br />

inf S<br />

lim inf<br />

n→∞ a n<br />

greatest b ∈ R such that b ≤<br />

s, ∀s ∈ S.<br />

lim inf{a i | i ≥ n, i ∈ N}.<br />

n→∞<br />

Theoretical Computer Science Cheat Sheet<br />

n∑<br />

i =<br />

i=1<br />

In general:<br />

n∑<br />

i=1<br />

i=1<br />

n(n + 1)<br />

,<br />

2<br />

i m = 1<br />

m + 1<br />

n−1<br />

∑<br />

i m = 1<br />

m + 1<br />

i=0<br />

n∑<br />

i 2 =<br />

i=1<br />

[<br />

(n + 1) m+1 − 1 −<br />

m∑<br />

( m + 1<br />

k=0<br />

k<br />

Series<br />

n(n + 1)(2n + 1)<br />

,<br />

6<br />

n∑<br />

i=1<br />

i 3 = n2 (n + 1) 2<br />

.<br />

4<br />

n∑ (<br />

(i + 1) m+1 − i m+1 − (m + 1)i m)]<br />

i=1<br />

)<br />

B k n m+1−k .<br />

Geometric series:<br />

n∑<br />

c i = cn+1 − 1<br />

c − 1 , c ≠ 1, ∑<br />

∞ c i = 1<br />

1 − c , ∑<br />

∞ c i =<br />

i=0<br />

i=0<br />

i=1<br />

n∑<br />

ic i = ncn+2 − (n + 1)c n+1 + c<br />

∞∑<br />

(c − 1) 2 , c ≠ 1, ic i =<br />

Harmonic series:<br />

n∑ 1<br />

H n =<br />

i ,<br />

n ∑<br />

i=0<br />

n(n + 1) n(n − 1)<br />

iH i = H n − .<br />

2<br />

4<br />

n∑<br />

( ( ) (<br />

i n + 1<br />

H i =<br />

m)<br />

m + 1<br />

c , |c| < 1,<br />

1 − c<br />

c<br />

, |c| < 1.<br />

(1 − c)<br />

2<br />

lim sup a n lim sup{a i | i ≥ n, i ∈ N}.<br />

i=1 i=1<br />

n→∞<br />

n→∞<br />

( n∑<br />

H i = (n + 1)H n − n,<br />

H n+1 − 1 )<br />

n<br />

k)<br />

Combinations: Size k subsets<br />

of a size n set.<br />

m + 1<br />

.<br />

i=1<br />

i=1<br />

[ n<br />

]<br />

(<br />

k<br />

Stirling numbers (1st kind): n n!<br />

Arrangements of an n element<br />

set into k cycles.<br />

( n<br />

1. =<br />

k)<br />

(n − k)!k! , 2. ∑<br />

n ( ( ( )<br />

n n n<br />

= 2<br />

k)<br />

n , 3. = ,<br />

k)<br />

n − k<br />

k=0<br />

4. =<br />

k)<br />

n ( )<br />

( ( ) ( )<br />

{ n − 1<br />

n n − 1 n − 1<br />

n<br />

}<br />

, 5. = + ,<br />

k<br />

Stirling numbers (2nd kind):<br />

k k − 1<br />

k)<br />

k k − 1<br />

Partitions of an n element ( )( ) ( )( )<br />

n m n n − k<br />

n∑<br />

( ) ( )<br />

r + k r + n + 1<br />

set into k non-empty sets. 6.<br />

=<br />

, 7.<br />

=<br />

,<br />

⟨ m k k m − k<br />

k<br />

n<br />

n<br />

⟩<br />

k=0<br />

n∑<br />

( ( )<br />

k n + 1<br />

n∑<br />

( )( ) ( )<br />

k<br />

1st order Eulerian numbers:<br />

r s r + s<br />

Permutations π 1 π 2 . . . π n on 8. = , 9.<br />

= ,<br />

m)<br />

m + 1<br />

k n − k n<br />

{1, 2, . . . , n} with k ascents.<br />

k=0<br />

( ( )<br />

k=0<br />

{ } {<br />

⟨ n<br />

⟩<br />

n k − n − 1<br />

n n<br />

10. = (−1)<br />

k)<br />

k , 11. = = 1,<br />

k<br />

2nd order Eulerian numbers.<br />

k<br />

1 n}<br />

C { }<br />

{ } { } { }<br />

n Catalan Numbers: Binary<br />

n n n − 1 n − 1<br />

trees with n + 1 vertices. 12. = 2 n−1 − 1, 13. = k + ,<br />

2 k k k − 1<br />

[ ]<br />

[ ]<br />

[ [ ] { }<br />

n n n n n<br />

14. = (n − 1)!, 15. = (n − 1)!H n−1 , 16. = 1, 17. ≥ ,<br />

1 2 n]<br />

k k<br />

[ ] [ ] [ ] { } [ ] ( n n − 1 n − 1<br />

n n n<br />

n∑<br />

[ ] n<br />

18. = (n − 1) + , 19. = = , 20. = n!, 21. C n =<br />

k k k − 1<br />

n − 1 n − 1 2)<br />

1 ) 2n<br />

,<br />

k n + 1(<br />

n<br />

⟨ ⟩ ⟨ ⟩<br />

⟨ ⟩ ⟨ ⟩<br />

⟨ ⟩ k=0 ⟨ ⟩ ⟨ ⟩<br />

n n<br />

n n<br />

n n − 1<br />

n − 1<br />

22. = = 1, 23. =<br />

, 24. = (k + 1) + (n − k) ,<br />

0 n − 1<br />

k n − 1 − k<br />

k k<br />

k − 1<br />

⟨ ⟩ 0<br />

{ ⟨ ⟩<br />

⟨ ⟩<br />

( )<br />

1 if k = 0,<br />

n n n + 1<br />

25. =<br />

26. = 2 n − n − 1, 27. = 3 n − (n + 1)2 n + ,<br />

k 0 otherwise<br />

1 2 2<br />

n∑<br />

⟨ ⟩( )<br />

⟨ n x + k<br />

n<br />

m∑<br />

( )<br />

{ n + 1<br />

n<br />

n∑<br />

⟨ ⟩( )<br />

n k<br />

28. x n =<br />

, 29. =<br />

(m + 1 − k)<br />

k n<br />

m⟩<br />

n (−1) k , 30. m! =<br />

,<br />

k<br />

m}<br />

k n − m<br />

k=0<br />

k=0<br />

k=0<br />

⟨ n<br />

n∑<br />

{ }( )<br />

⟨ ⟩<br />

⟨ ⟩<br />

n n − k<br />

n n<br />

31. =<br />

(−1)<br />

m⟩<br />

n−k−m k!, 32. = 1, 33. = 0 for n ≠ 0,<br />

k m<br />

0<br />

n<br />

k=0<br />

⟨ ⟩ ⟨ ⟩<br />

⟨ ⟩<br />

n n − 1<br />

n − 1<br />

n∑<br />

⟨ ⟩ n<br />

34. = (k + 1) + (2n − 1 − k) , 35.<br />

= (2n)n<br />

k<br />

k<br />

k − 1<br />

k 2 n ,<br />

k=0<br />

{ } x<br />

n∑<br />

⟨ ⟩( )<br />

{ }<br />

n x + n − 1 − k<br />

n + 1<br />

36. =<br />

, 37.<br />

= ∑ ( ){ n k<br />

n∑<br />

{ k<br />

= (m + 1)<br />

x − n k 2n<br />

m + 1 k m}<br />

m}<br />

n−k ,<br />

k=0<br />

k<br />

k=0


38.<br />

40.<br />

42.<br />

44.<br />

46.<br />

48.<br />

Theoretical Computer Science Cheat Sheet<br />

Identities Cont.<br />

[ ] n + 1<br />

= ∑ [ ]( n k<br />

n∑<br />

[ k<br />

n∑<br />

] [ ]<br />

= n<br />

m + 1 k m)<br />

m]<br />

n−k 1 k x<br />

n∑<br />

⟨ ⟩( )<br />

n x + k<br />

= n!<br />

, 39. =<br />

,<br />

k![<br />

m<br />

x − n k 2n<br />

{<br />

k<br />

k=0<br />

k=0<br />

k=0<br />

n<br />

=<br />

m}<br />

∑ ( ){ }<br />

[ n k + 1<br />

n<br />

(−1) n−k , 41. =<br />

k m + 1<br />

m]<br />

∑ [ ]( )<br />

n + 1 k<br />

(−1) m−k ,<br />

k + 1 m<br />

k<br />

k<br />

{ }<br />

m + n + 1<br />

m∑<br />

{ }<br />

[ ]<br />

n + k<br />

m + n + 1<br />

m∑<br />

[ ] n + k<br />

= k , 43.<br />

= k(n + k) ,<br />

m<br />

k<br />

m<br />

k<br />

(<br />

k=0<br />

k=0<br />

n<br />

=<br />

m)<br />

∑ { }[ ]<br />

( n + 1 k n<br />

(−1) m−k , 45. (n − m)! =<br />

k + 1 m<br />

m)<br />

∑ [ ]{ }<br />

n + 1 k<br />

(−1) m−k , for n ≥ m,<br />

k + 1 m<br />

{ }<br />

k<br />

k<br />

n<br />

= ∑ ( )( )[ ] [ ]<br />

m − n m + n m + k<br />

n<br />

, 47. = ∑ ( )( ){ }<br />

m − n m + n m + k<br />

,<br />

n − m m + k n + k k<br />

n − m m + k n + k k<br />

{ }(<br />

k<br />

)<br />

k<br />

n l + m<br />

= ∑ { }{ }( [ ]( )<br />

k n − k n n l + m<br />

, 49.<br />

=<br />

l + m l<br />

l m k)<br />

∑ [ ][ ]( k n − k n<br />

.<br />

l + m l<br />

l m k)<br />

k<br />

k<br />

Trees<br />

Every tree with n<br />

vertices has n − 1<br />

edges.<br />

Kraft inequality:<br />

If the depths<br />

of the leaves of<br />

a binary tree are<br />

d 1 , . . . , d n :<br />

n∑<br />

2 −d i<br />

≤ 1,<br />

i=1<br />

and equality holds<br />

only if every internal<br />

node has 2<br />

sons.<br />

Master method:<br />

T (n) = aT (n/b) + f(n), a ≥ 1, b > 1<br />

If ∃ϵ > 0 such that f(n) = O(n log b a−ϵ )<br />

then<br />

T (n) = Θ(n log b a ).<br />

If f(n) = Θ(n log b a ) then<br />

T (n) = Θ(n log b a log 2 n).<br />

If ∃ϵ > 0 such that f(n) = Ω(n log b a+ϵ ),<br />

and ∃c < 1 such that af(n/b) ≤ cf(n)<br />

for large n, then<br />

T (n) = Θ(f(n)).<br />

Substitution (example): Consider the<br />

following recurrence<br />

T i+1 = 2 2i · T 2 i , T 1 = 2.<br />

Note that T i is always a power of two.<br />

Let t i = log 2 T i . Then we have<br />

t i+1 = 2 i + 2t i , t 1 = 1.<br />

Let u i = t i /2 i . Dividing both sides of<br />

the previous equation by 2 i+1 we get<br />

t i+1 2i<br />

=<br />

2i+1 2 i+1 + t i<br />

2 i .<br />

Substituting we find<br />

u i+1 = 1 2 + u i, u 1 = 1 2 ,<br />

which is simply u i = i/2. So we find<br />

that T i has the closed form T i = 2 i2i−1 .<br />

Summing factors (example): Consider<br />

the following recurrence<br />

T (n) = 3T (n/2) + n, T (1) = 1.<br />

Rewrite so that all terms involving T<br />

are on the left side<br />

T (n) − 3T (n/2) = n.<br />

Now expand the recurrence, and choose<br />

a factor which makes the left side “telescope”<br />

Recurrences<br />

1 ( T (n) − 3T (n/2) = n )<br />

3 ( T (n/2) − 3T (n/4) = n/2 )<br />

. . .<br />

3 log n−1( 2<br />

T (2) − 3T (1) = 2 )<br />

Let m = log 2 n. Summing the left side<br />

we get T (n) − 3 m T (1) = T (n) − 3 m =<br />

T (n) − n k where k = log 2 3 ≈ 1.58496.<br />

Summing the right side we get<br />

m−1<br />

∑<br />

m−1<br />

n ∑ (<br />

2 i 3i = n 3<br />

) i<br />

2 .<br />

i=0<br />

i=0<br />

Let c = 3 2<br />

. Then we have<br />

m−1<br />

∑<br />

( c<br />

n c i m )<br />

− 1<br />

= n<br />

c − 1<br />

i=0<br />

= 2n(c log 2 n − 1)<br />

= 2n(c (k−1) log c n − 1)<br />

= 2n k − 2n,<br />

and so T (n) = 3n k − 2n. Full history recurrences<br />

can often be changed to limited<br />

history ones (example): Consider<br />

∑i−1<br />

T i = 1 + T j , T 0 = 1.<br />

Note that<br />

j=0<br />

T i+1 = 1 +<br />

Subtracting we find<br />

T i+1 − T i = 1 +<br />

= T i .<br />

i∑<br />

T j .<br />

j=0<br />

i∑ ∑i−1<br />

T j − 1 −<br />

j=0<br />

And so T i+1 = 2T i = 2 i+1 .<br />

j=0<br />

T j<br />

Generating functions:<br />

1. Multiply both sides of the equation<br />

by x i .<br />

2. Sum both sides over all i for<br />

which the equation is valid.<br />

3. Choose a generating function<br />

G(x). Usually G(x) = ∑ ∞<br />

i=0 xi g i .<br />

3. Rewrite the equation in terms of<br />

the generating function G(x).<br />

4. Solve for G(x).<br />

5. The coefficient of x i in G(x) is g i .<br />

Example:<br />

g i+1 = 2g i + 1, g 0 = 0.<br />

Multiply and sum:<br />

∑<br />

i≥0<br />

g i+1 x i = ∑ i≥0<br />

2g i x i + ∑ i≥0<br />

x i .<br />

We choose G(x) = ∑ i≥0 xi g i . Rewrite<br />

in terms of G(x):<br />

G(x) − g 0<br />

= 2G(x) + ∑ x i .<br />

x<br />

i≥0<br />

Simplify:<br />

G(x)<br />

= 2G(x) + 1<br />

x<br />

1 − x .<br />

Solve for G(x):<br />

x<br />

G(x) =<br />

(1 − x)(1 − 2x) .<br />

Expand this ( using partial fractions:<br />

2<br />

G(x) = x<br />

1 − 2x − 1 )<br />

1 − x<br />

⎛<br />

⎞<br />

= x ⎝2 ∑ 2 i x i − ∑ x i ⎠<br />

i≥0 i≥0<br />

So g i = 2 i − 1.<br />

= ∑ i≥0(2 i+1 − 1)x i+1 .


Theoretical Computer Science Cheat Sheet<br />

π ≈ 3.14159, e ≈ 2.71828, γ ≈ 0.57721, ϕ = 1+√ 5<br />

2<br />

≈ 1.61803, ˆϕ =<br />

1− √ 5<br />

2<br />

≈ −.61803<br />

i 2 i p i General Probability<br />

1 2 2 Bernoulli Numbers (B i = 0, odd i ≠ 1):<br />

2 4 3<br />

3 8 5<br />

4 16 7<br />

5 32 11<br />

6 64 13<br />

7 128 17<br />

8 256 19<br />

9 512 23<br />

10 1,024 29<br />

11 2,048 31<br />

12 4,096 37<br />

13 8,192 41<br />

14 16,384 43<br />

15 32,768 47<br />

16 65,536 53<br />

17 131,072 59<br />

18 262,144 61<br />

19 524,288 67<br />

20 1,048,576 71<br />

21 2,097,152 73<br />

22 4,194,304 79<br />

23 8,388,608 83<br />

24 16,777,216 89<br />

25 33,554,432 97<br />

26 67,108,864 101<br />

27 134,217,728 103<br />

B 0 = 1, B 1 = − 1 2 , B 2 = 1 6 , B 4 = − 1 30 ,<br />

B 6 = 1<br />

42 , B 8 = − 1<br />

30 , B 10 = 5 66 .<br />

Change of base, quadratic formula:<br />

log b x = log a x<br />

log a b ,<br />

Euler’s number e:<br />

−b ± √ b 2 − 4ac<br />

.<br />

2a<br />

e = 1 + 1 2 + 1 6 + 1 24 + 1<br />

120<br />

(<br />

+ · · ·<br />

lim 1 + x n<br />

= e<br />

n→∞ n) x .<br />

( )<br />

1 +<br />

1 n (<br />

n < e < 1 +<br />

1 n+1<br />

n)<br />

.<br />

( )<br />

1 +<br />

1 n e<br />

n = e −<br />

2n + 11e ( ) 1<br />

24n 2 − O n 3 .<br />

Harmonic numbers:<br />

1, 3 2 , 11<br />

6 , 25<br />

12 , 137<br />

60 , 49<br />

20 , 363<br />

140 , 761<br />

280 , 7129<br />

2520 , . . .<br />

ln n < H n < ln n + 1,<br />

( 1<br />

H n = ln n + γ + O .<br />

n)<br />

Factorial, Stirling’s approximation:<br />

1, 2, 6, 24, 120, 720, 5040, 40320, 362880, . . .<br />

n! = √ ( ) n ( ( n 1<br />

2πn 1 + Θ .<br />

e n))<br />

Ackermann’s ⎧ function and inverse:<br />

⎨ 2 j i = 1<br />

a(i, j) = a(i − 1, 2) j = 1<br />

⎩<br />

a(i − 1, a(i, j − 1)) i, j ≥ 2<br />

α(i) = min{j | a(j, j) ≥ i}.<br />

28 268,435,456 107 Binomial distribution:<br />

(<br />

29 536,870,912 109<br />

n<br />

Pr[X = k] = p<br />

k)<br />

k q n−k , q = 1 − p,<br />

30 1,073,741,824 113<br />

n∑<br />

(<br />

31 2,147,483,648 127<br />

n<br />

E[X] = k p<br />

k)<br />

k q n−k = np.<br />

32 4,294,967,296 131<br />

k=1<br />

Pascal’s Triangle<br />

Poisson distribution:<br />

Pr[X = k] = e−λ λ k<br />

1<br />

, E[X] = λ.<br />

k!<br />

1 1<br />

Normal (Gaussian) distribution:<br />

1 2 1<br />

p(x) = √ 1 e −(x−µ)2 /2σ 2 , E[X] = µ.<br />

1 3 3 1<br />

2πσ<br />

1 4 6 4 1<br />

The “coupon collector”: We are given a<br />

1 5 10 10 5 1<br />

random coupon each day, and there are n<br />

different types of coupons. The distribution<br />

of coupons is uniform. The expected<br />

1 6 15 20 15 6 1<br />

1 7 21 35 35 21 7 1<br />

number of days to pass before we to collect<br />

all n types is<br />

1 8 28 56 70 56 28 8 1<br />

1 9 36 84 126 126 84 36 9 1<br />

nH n .<br />

1 10 45 120 210 252 210 120 45 10 1<br />

Continuous distributions: If<br />

Pr[a < X < b] =<br />

∫ b<br />

a<br />

p(x) dx,<br />

then p is the probability density function of<br />

X. If<br />

Pr[X < a] = P (a),<br />

then P is the distribution function of X. If<br />

P and p both exist then<br />

P (a) =<br />

∫ a<br />

−∞<br />

p(x) dx.<br />

Expectation: If X is discrete<br />

E[g(X)] = ∑ g(x) Pr[X = x].<br />

x<br />

If X continuous then<br />

E[g(X)] =<br />

∫ ∞<br />

−∞<br />

g(x)p(x) dx =<br />

Variance, standard deviation:<br />

∫ ∞<br />

−∞<br />

VAR[X] = E[X 2 ] − E[X] 2 ,<br />

g(x) dP (x).<br />

σ = √ VAR[X].<br />

For events A and B:<br />

Pr[A ∨ B] = Pr[A] + Pr[B] − Pr[A ∧ B]<br />

Pr[A ∧ B] = Pr[A] · Pr[B],<br />

iff A and B are independent.<br />

Pr[A ∧ B]<br />

Pr[A|B] =<br />

Pr[B]<br />

For random variables X and Y :<br />

E[X · Y ] = E[X] · E[Y ],<br />

if X and Y are independent.<br />

E[X + Y ] = E[X] + E[Y ],<br />

E[cX] = c E[X].<br />

Bayes’ theorem:<br />

Pr[B|A i ] Pr[A i ]<br />

Pr[A i |B] = ∑ n<br />

j=1 Pr[A j] Pr[B|A j ] .<br />

Inclusion-exclusion:<br />

[ ∨<br />

n ] n∑<br />

Pr X i = Pr[X i ] +<br />

i=1<br />

i=1<br />

n∑<br />

(−1) k+1<br />

k=2<br />

Moment inequalities:<br />

∑<br />

i i


Theoretical Computer Science Cheat Sheet<br />

Trigonometry Matrices More Trig.<br />

Multiplication:<br />

(0,1)<br />

C = A · B,<br />

n∑<br />

c i,j = a i,k b k,j .<br />

b<br />

(cos θ, sin θ)<br />

k=1<br />

C<br />

A<br />

θ<br />

Determinants: det A ≠ 0 iff A is non-singular.<br />

(-1,0) (1,0)<br />

det A · B = det A · det B,<br />

c a<br />

(0,-1)<br />

B<br />

det A = ∑ n∏<br />

sign(π)a i,π(i) .<br />

Pythagorean theorem:<br />

π i=1<br />

C 2 = A 2 + B 2 .<br />

2 × 2 and 3 × 3 determinant:<br />

Definitions:<br />

∣ a b<br />

c d ∣ = ad − bc,<br />

sin a = A/C, cos a = B/C,<br />

csc a = C/A, sec a = C/B,<br />

a b c<br />

∣ ∣ ∣ ∣∣∣ tan a = sin a<br />

cos a = A B , cos a<br />

cot a =<br />

sin a = B d e f<br />

A . ∣ g h i ∣ = g b c<br />

∣∣∣ e f ∣ − h a c<br />

∣∣∣ d f ∣ + i a b<br />

d e ∣<br />

aei + bfg + cdh<br />

Area, radius of inscribed circle:<br />

=<br />

− ceg − fha − ibd.<br />

1<br />

2 AB, AB<br />

A + B + C .<br />

Permanents:<br />

Identities:<br />

perm A = ∑ n∏<br />

a i,π(i) .<br />

sin x = 1<br />

csc x , cos x = 1<br />

π<br />

sec x ,<br />

i=1<br />

Hyperbolic Functions<br />

tan x = 1<br />

cot x , sin2 x + cos 2 x = 1,<br />

Definitions:<br />

sinh x = ex − e −x<br />

, cosh x = ex + e −x<br />

,<br />

1 + tan 2 x = sec 2 x, 1 + cot 2 x = csc 2 x,<br />

sin x = cos ( π<br />

2 − x) , sin x = sin(π − x),<br />

cos x = − cos(π − x),<br />

tan x = cot ( π<br />

2 − x) ,<br />

cot x = − cot(π − x), csc x = cot x 2<br />

− cot x,<br />

sin(x ± y) = sin x cos y ± cos x sin y,<br />

cos(x ± y) = cos x cos y ∓ sin x sin y,<br />

tan x ± tan y<br />

tan(x ± y) =<br />

1 ∓ tan x tan y ,<br />

cot x cot y ∓ 1<br />

cot(x ± y) =<br />

cot x ± cot y ,<br />

sin 2x = 2 sin x cos x, sin 2x = 2 tan x<br />

1 + tan 2 x ,<br />

cos 2x = cos 2 x − sin 2 x, cos 2x = 2 cos 2 x − 1,<br />

cos 2x = 1 − 2 sin 2 x,<br />

tan 2x =<br />

cos 2x = 1 − tan2 x<br />

1 + tan 2 x ,<br />

2 tan x<br />

1 − tan 2 x , cot 2x = cot2 x − 1<br />

2 cot x ,<br />

sin(x + y) sin(x − y) = sin 2 x − sin 2 y,<br />

cos(x + y) cos(x − y) = cos 2 x − sin 2 y.<br />

Euler’s equation:<br />

e ix = cos x + i sin x, e iπ = −1.<br />

v2.02 c⃝1994 by Steve Seiden<br />

sseiden@acm.org<br />

http://www.csc.lsu.edu/~seiden<br />

2<br />

2<br />

tanh x = ex − e −x<br />

1<br />

e x , csch x =<br />

+ e−x sinh x ,<br />

sech x = 1<br />

cosh x , coth x = 1<br />

tanh x .<br />

Identities:<br />

cosh 2 x − sinh 2 x = 1, tanh 2 x + sech 2 x = 1,<br />

coth 2 x − csch 2 x = 1, sinh(−x) = − sinh x,<br />

cosh(−x) = cosh x, tanh(−x) = − tanh x,<br />

sinh(x + y) = sinh x cosh y + cosh x sinh y,<br />

cosh(x + y) = cosh x cosh y + sinh x sinh y,<br />

sinh 2x = 2 sinh x cosh x,<br />

cosh 2x = cosh 2 x + sinh 2 x,<br />

cosh x + sinh x = e x , cosh x − sinh x = e −x ,<br />

(cosh x + sinh x) n = cosh nx + sinh nx, n ∈ Z,<br />

2 sinh 2 x 2 = cosh x − 1, 2 cosh2 x 2<br />

= cosh x + 1.<br />

θ sin θ cos θ tan θ<br />

0 0 1 0<br />

π<br />

6<br />

π<br />

4<br />

π<br />

3<br />

π<br />

1<br />

2<br />

√<br />

2<br />

2<br />

√<br />

3<br />

2<br />

√ √<br />

3 3<br />

2 3<br />

√<br />

2<br />

2<br />

1<br />

√<br />

1<br />

2 3<br />

2<br />

1 0 ∞<br />

. . . in mathematics<br />

you don’t understand<br />

things, you<br />

just get used to<br />

them.<br />

– J. von Neumann<br />

b<br />

C<br />

h<br />

a<br />

A c<br />

Law of cosines:<br />

B<br />

c 2 = a 2 +b 2 −2ab cos C.<br />

Area:<br />

A = 1 2 hc,<br />

= 1 2ab sin C,<br />

= c2 sin A sin B<br />

.<br />

2 sin C<br />

Heron’s formula:<br />

A = √ s · s a · s b · s c ,<br />

s = 1 2<br />

(a + b + c),<br />

s a = s − a,<br />

s b = s − b,<br />

s c = s − c.<br />

More identities:<br />

√<br />

1 − cos x<br />

sin x 2 = ,<br />

2<br />

√<br />

1 + cos x<br />

cos x 2 = ,<br />

2<br />

√<br />

1 − cos x<br />

tan x 2 = 1 + cos x ,<br />

= 1 − cos x<br />

sin x ,<br />

= sin x<br />

1 + cos x ,<br />

cot x 2 = √<br />

1 + cos x<br />

1 − cos x ,<br />

= 1 + cos x<br />

sin x ,<br />

= sin x<br />

1 − cos x ,<br />

sin x = eix − e −ix<br />

,<br />

2i<br />

cos x = eix + e −ix<br />

,<br />

2<br />

tan x = −i eix − e −ix<br />

e ix + e −ix ,<br />

= −i e2ix − 1<br />

e 2ix + 1 ,<br />

sinh ix<br />

sin x = ,<br />

i<br />

cos x = cosh ix,<br />

tanh ix<br />

tan x = .<br />

i


Number Theory<br />

The Chinese remainder theorem: There exists<br />

a number C such that:<br />

C ≡ r 1 mod m 1<br />

.<br />

.<br />

.<br />

C ≡ r n mod m n<br />

if m i and m j are relatively prime for i ≠ j.<br />

Euler’s function: ϕ(x) is the number of<br />

positive integers less than x relatively<br />

prime to x. If ∏ n<br />

i=1 pe i<br />

i is the prime factorization<br />

of x then<br />

n∏<br />

ϕ(x) = p ei−1<br />

i (p i − 1).<br />

i=1<br />

Euler’s theorem: If a and b are relatively<br />

prime then<br />

1 ≡ a ϕ(b) mod b.<br />

Fermat’s theorem:<br />

1 ≡ a p−1 mod p.<br />

The Euclidean algorithm: if a > b are integers<br />

then<br />

gcd(a, b) = gcd(a mod b, b).<br />

If ∏ n<br />

then<br />

i=1 pe i<br />

i<br />

is the prime factorization of x<br />

S(x) = ∑ d|x<br />

d =<br />

n∏<br />

i=1<br />

p e i+1<br />

i − 1<br />

p i − 1 .<br />

Perfect Numbers: x is an even perfect number<br />

iff x = 2 n−1 (2 n −1) and 2 n −1 is prime.<br />

Wilson’s theorem: n is a prime iff<br />

(n − 1)! ≡ −1 mod n.<br />

Möbius ⎧inversion:<br />

1 if i = 1.<br />

⎪⎨<br />

0 if i is not square-free.<br />

µ(i) =<br />

⎪⎩ (−1) r if i is the product of<br />

r distinct primes.<br />

If<br />

then<br />

G(a) = ∑ d|a<br />

F (a) = ∑ d|a<br />

F (d),<br />

( a<br />

µ(d)G .<br />

d)<br />

Prime numbers:<br />

ln ln n<br />

p n = n ln n + n ln ln n − n + n<br />

( )<br />

ln n<br />

n<br />

+ O ,<br />

ln n<br />

π(n) =<br />

n<br />

ln n + n<br />

(ln n) 2 + 2!n<br />

(ln n)<br />

( )<br />

3<br />

n<br />

+ O<br />

(ln n) 4 .<br />

Theoretical Computer Science Cheat Sheet<br />

Definitions:<br />

Graph Theory<br />

Loop An edge connecting a vertex<br />

to itself.<br />

Directed Each edge has a direction.<br />

Simple Graph with no loops or<br />

multi-edges.<br />

Walk A sequence v 0 e 1 v 1 . . . e l v l .<br />

Trail A walk with distinct edges.<br />

Path A trail with distinct<br />

vertices.<br />

Connected A graph where there exists<br />

a path between any two<br />

vertices.<br />

Component A maximal connected<br />

subgraph.<br />

Tree A connected acyclic graph.<br />

Free tree A tree with no root.<br />

DAG Directed acyclic graph.<br />

Eulerian Graph with a trail visiting<br />

each edge exactly once.<br />

Hamiltonian Graph with a cycle visiting<br />

each vertex exactly once.<br />

Cut A set of edges whose removal<br />

increases the number<br />

of components.<br />

Cut-set A minimal cut.<br />

Cut edge A size 1 cut.<br />

k-Connected A graph connected with<br />

the removal of any k − 1<br />

vertices.<br />

k-Tough ∀S ⊆ V, S ≠ ∅ we have<br />

k · c(G − S) ≤ |S|.<br />

k-Regular A graph where all vertices<br />

have degree k.<br />

k-Factor A k-regular spanning<br />

subgraph.<br />

Matching A set of edges, no two of<br />

which are adjacent.<br />

Clique A set of vertices, all of<br />

which are adjacent.<br />

Ind. set A set of vertices, none of<br />

which are adjacent.<br />

Vertex cover A set of vertices which<br />

cover all edges.<br />

Planar graph A graph which can be embeded<br />

in the plane.<br />

Plane graph An embedding of a planar<br />

graph.<br />

∑<br />

deg(v) = 2m.<br />

v∈V<br />

If G is planar then n − m + f = 2, so<br />

f ≤ 2n − 4, m ≤ 3n − 6.<br />

Any planar graph has a vertex with degree<br />

≤ 5.<br />

Notation:<br />

E(G) Edge set<br />

V (G) Vertex set<br />

c(G) Number of components<br />

G[S] Induced subgraph<br />

deg(v) Degree of v<br />

∆(G) Maximum degree<br />

δ(G) Minimum degree<br />

χ(G) Chromatic number<br />

χ E (G) Edge chromatic number<br />

G c Complement graph<br />

K n Complete graph<br />

K n1 ,n 2<br />

Complete bipartite graph<br />

r(k, l) Ramsey number<br />

Geometry<br />

Projective coordinates: triples<br />

(x, y, z), not all x, y and z zero.<br />

(x, y, z) = (cx, cy, cz) ∀c ≠ 0.<br />

Cartesian<br />

Projective<br />

(x, y) (x, y, 1)<br />

y = mx + b (m, −1, b)<br />

x = c (1, 0, −c)<br />

Distance formula, L p and L ∞<br />

metric:<br />

√<br />

(x1 − x 0 ) 2 + (y 1 − y 0 ) 2 ,<br />

[<br />

|x1 − x 0 | p + |y 1 − y 0 | p] 1/p<br />

,<br />

[<br />

lim |x1 − x 0 | p + |y 1 − y 0 | p] 1/p<br />

.<br />

p→∞<br />

Area of triangle (x 0 , y 0 ), (x 1 , y 1 )<br />

and (x 2 , y 2 ):<br />

∣ ∣<br />

1 ∣∣∣<br />

2 abs x 1 − x 0 y 1 − y 0 ∣∣∣<br />

.<br />

x 2 − x 0 y 2 − y 0<br />

Angle formed by three points:<br />

θ<br />

(0, 0)<br />

l 2<br />

l 1<br />

(x 2 , y 2 )<br />

(x 1 , y 1 )<br />

cos θ = (x 1, y 1 ) · (x 2 , y 2 )<br />

.<br />

l 1 l 2<br />

Line through two points (x 0 , y 0 )<br />

and (x 1 , y 1 ):<br />

x y 1<br />

x 0 y 0 1<br />

∣ x 1 y 1 1 ∣ = 0.<br />

Area of circle, volume of sphere:<br />

A = πr 2 , V = 4 3 πr3 .<br />

If I have seen farther than others,<br />

it is because I have stood on the<br />

shoulders of giants.<br />

– Issac Newton


Wallis’ identity:<br />

π = 2 · 2 · 2 · 4 · 4 · 6 · 6 · · ·<br />

1 · 3 · 3 · 5 · 5 · 7 · · ·<br />

π<br />

Brouncker’s continued fraction expansion:<br />

π<br />

4 = 1 + 1 2<br />

3<br />

2 + 2<br />

2+ 52<br />

2+<br />

2+···<br />

72<br />

Gregrory’s series:<br />

π<br />

4 = 1 − 1 3 + 1 5 − 1 7 + 1 9 − · · ·<br />

Newton’s series:<br />

π<br />

6 = 1 2 + 1<br />

2 · 3 · 2 3 + 1 · 3<br />

2 · 4 · 5 · 2 5 + · · ·<br />

Sharp’s series:<br />

π<br />

6 = √ 1 (<br />

1 − 1<br />

3 3 1 · 3 + 1<br />

3 2 · 5 − 1 )<br />

3 3 · 7 + · · ·<br />

Euler’s series:<br />

π 2<br />

6 = 1 1 2 + 1 2 2 + 1 3 2 + 1 4 2 + 1 5 2 + · · ·<br />

π 2<br />

8 = 1 1 2 + 1 3 2 + 1 5 2 + 1 7 2 + 1 9 2 + · · ·<br />

π 2<br />

12 = 1 1 2 − 1 2 2 + 1 3 2 − 1 4 2 + 1 5 2 − · · ·<br />

Partial Fractions<br />

Let N(x) and D(x) be polynomial functions<br />

of x. We can break down<br />

N(x)/D(x) using partial fraction expansion.<br />

First, if the degree of N is greater<br />

than or equal to the degree of D, divide<br />

N by D, obtaining<br />

N(x)<br />

D(x) = Q(x) + N ′ (x)<br />

D(x) ,<br />

where the degree of N ′ is less than that of<br />

D. Second, factor D(x). Use the following<br />

rules: For a non-repeated factor:<br />

N(x)<br />

(x − a)D(x) = A<br />

x − a + N ′ (x)<br />

D(x) ,<br />

where<br />

A =<br />

[ ] N(x)<br />

.<br />

D(x)<br />

x=a<br />

For a repeated factor:<br />

m−1<br />

N(x)<br />

(x − a) m D(x) = ∑ A k (x)<br />

(x − a) m−k +N′ D(x) ,<br />

where<br />

A k = 1 k!<br />

k=0<br />

[ ( )]<br />

d<br />

k N(x)<br />

dx k .<br />

D(x)<br />

x=a<br />

The reasonable man adapts himself to the<br />

world; the unreasonable persists in trying<br />

to adapt the world to himself. Therefore<br />

all progress depends on the unreasonable.<br />

– George Bernard Shaw<br />

Theoretical Computer Science Cheat Sheet<br />

Derivatives:<br />

1. d(cu)<br />

dx<br />

4. d(un )<br />

dx<br />

7. d(cu )<br />

dx<br />

9.<br />

11.<br />

13.<br />

15.<br />

17.<br />

19.<br />

21.<br />

23.<br />

25.<br />

27.<br />

29.<br />

d(sin u)<br />

dx<br />

d(tan u)<br />

dx<br />

d(sec u)<br />

dx<br />

Calculus<br />

= cdu<br />

d(u + v)<br />

, 2. = du<br />

dx dx<br />

du<br />

= nun−1<br />

dx ,<br />

du<br />

= (ln c)cu<br />

dx<br />

d(arcsin u)<br />

dx<br />

d(arctan u)<br />

dx<br />

d(arcsec u)<br />

dx<br />

d(sinh u)<br />

dx<br />

d(tanh u)<br />

dx<br />

d(sech u)<br />

dx<br />

d(arcsinh u)<br />

dx<br />

d(arctanh u)<br />

dx<br />

dx + dv<br />

dx ,<br />

d(u/v)<br />

5. = v( du<br />

dx<br />

dx<br />

d(uv)<br />

3.<br />

dx<br />

= u dv<br />

dx + v du<br />

dx ,<br />

) (<br />

− u<br />

dv<br />

)<br />

dx<br />

v 2 , 6. d(ecu )<br />

dx<br />

, 8.<br />

d(ln u)<br />

dx<br />

cu du<br />

= ce<br />

dx ,<br />

= 1 du<br />

u dx ,<br />

= cos u du<br />

d(cos u)<br />

, 10. = − sin u du<br />

dx dx<br />

dx ,<br />

= sec 2 u du<br />

d(cot u)<br />

, 12. = csc 2 u du<br />

dx dx<br />

dx ,<br />

= tan u sec u du<br />

d(csc u)<br />

, 14. = − cot u csc u du<br />

dx dx<br />

dx ,<br />

=<br />

1 du<br />

d(arccos u)<br />

√ , 16. = −1 du<br />

√<br />

1 − u<br />

2 dx dx 1 − u<br />

2 dx ,<br />

= 1 du<br />

1 + u 2 dx<br />

1<br />

=<br />

u √ du<br />

1 − u 2 dx<br />

, 18.<br />

d(arccot u)<br />

dx<br />

, 20.<br />

d(arccsc u)<br />

dx<br />

=<br />

= −1<br />

1 + u 2 du<br />

dx ,<br />

−1<br />

u √ du<br />

1 − u 2 dx ,<br />

= cosh u du<br />

d(cosh u)<br />

, 22. = sinh u du<br />

dx dx<br />

dx ,<br />

= sech 2 u du<br />

d(coth u)<br />

, 24. = − csch 2 u du<br />

dx dx<br />

dx ,<br />

= − sech u tanh u du<br />

d(csch u)<br />

, 26. = − csch u coth u du<br />

dx dx<br />

dx ,<br />

1 du<br />

d(arccosh u) 1 du<br />

= √ , 28. = √<br />

1 + u<br />

2 dx dx u2 − 1 dx ,<br />

= 1 du<br />

d(arccoth u)<br />

1 − u 2 , 30. = 1 du<br />

dx dx u 2 − 1 dx ,<br />

d(arcsech u) −1<br />

31. =<br />

dx u √ du<br />

d(arccsch u)<br />

, 32. =<br />

1 − u 2 dx dx<br />

Integrals:<br />

∫ ∫<br />

∫<br />

∫<br />

1. cu dx = c u dx, 2. (u + v) dx =<br />

3.<br />

6.<br />

8.<br />

10.<br />

12.<br />

14.<br />

−1<br />

|u| √ du<br />

1 + u 2 dx .<br />

∫<br />

u dx +<br />

v dx,<br />

∫<br />

x n dx = 1<br />

∫ ∫<br />

1<br />

n + 1 xn+1 , n ≠ −1, 4.<br />

x dx = ln x, 5. e x dx = e x ,<br />

∫<br />

∫<br />

dx<br />

1 + x 2 = arctan x, 7. u dv ∫<br />

dx dx = uv − v du<br />

dx dx,<br />

∫<br />

∫<br />

sin x dx = − cos x, 9. cos x dx = sin x,<br />

∫<br />

∫<br />

∫<br />

tan x dx = − ln | cos x|, 11.<br />

sec x dx = ln | sec x + tan x|, 13.<br />

arcsin x a dx = arcsin x a + √ a 2 − x 2 , a > 0,<br />

∫<br />

∫<br />

cot x dx = ln | cos x|,<br />

csc x dx = ln | csc x + cot x|,


15.<br />

17.<br />

19.<br />

21.<br />

23.<br />

25.<br />

26.<br />

29.<br />

33.<br />

36.<br />

∫<br />

∫<br />

∫<br />

∫<br />

∫<br />

∫<br />

∫<br />

∫<br />

∫<br />

∫<br />

Theoretical Computer Science Cheat Sheet<br />

Calculus Cont.<br />

arccos x a dx = arccos x a − √ a 2 − x 2 , a > 0, 16.<br />

∫<br />

arctan x a dx = x arctan x a − a 2 ln(a2 + x 2 ), a > 0,<br />

∫<br />

sin 2 ( )<br />

(ax)dx = 1<br />

2a ax − sin(ax) cos(ax) , 18. cos 2 )<br />

(ax)dx =<br />

2a( 1 ax + sin(ax) cos(ax) ,<br />

∫<br />

sec 2 x dx = tan x, 20. csc 2 x dx = − cot x,<br />

sin n x dx = − sinn−1 x cos x<br />

n<br />

∫<br />

−<br />

tan n x dx = tann−1 x<br />

n − 1<br />

sec n x dx = tan x secn−1 x<br />

n − 1<br />

+ n − 1<br />

n<br />

∫<br />

sin n−2 x dx, 22.<br />

tan n−2 x dx, n ≠ 1, 24.<br />

+ n − 2 ∫<br />

n − 1<br />

sec n−2 x dx, n ≠ 1,<br />

∫<br />

∫<br />

cos n x dx = cosn−1 x sin x<br />

n<br />

cot n x dx = − cotn−1 x<br />

n − 1<br />

+ n − 1 ∫<br />

cos n−2 x dx,<br />

n<br />

∫<br />

−<br />

cot n−2 x dx, n ≠ 1,<br />

csc n x dx = − cot x cscn−1 x<br />

+ n − 2 ∫<br />

∫<br />

∫<br />

csc n−2 x dx, n ≠ 1, 27. sinh x dx = cosh x, 28. cosh x dx = sinh x,<br />

n − 1 n − 1<br />

∫<br />

∫<br />

∫<br />

tanh x dx = ln | cosh x|, 30. coth x dx = ln | sinh x|, 31. sech x dx = arctan sinh x, 32. csch x dx = ln ∣ ∣tanh x ∣<br />

2<br />

,<br />

∫<br />

∫<br />

sinh 2 x dx = 1 4 sinh(2x) − 1 2 x,<br />

34. cosh 2 x dx = 1 4 sinh(2x) + 1 2 x,<br />

35. sech 2 x dx = tanh x,<br />

arcsinh x a dx = x arcsinh x a − √ x 2 + a 2 , a > 0, 37.<br />

∫<br />

arctanh x a dx = x arctanh x a + a 2 ln |a2 − x 2 |,<br />

38.<br />

39.<br />

40.<br />

42.<br />

43.<br />

46.<br />

48.<br />

50.<br />

52.<br />

54.<br />

56.<br />

58.<br />

60.<br />

⎧<br />

∫<br />

⎨ x arccosh x<br />

arccosh x a dx = a − √ x 2 + a 2 , if arccosh x a<br />

> 0 and a > 0,<br />

⎩<br />

x arccosh x a + √ x 2 + a 2 , if arccosh x a<br />

< 0 and a > 0,<br />

∫<br />

dx<br />

(<br />

√<br />

a2 + x = ln x + √ )<br />

a 2 + x 2 , a > 0,<br />

2<br />

∫<br />

∫<br />

∫<br />

dx<br />

√a2<br />

a 2 + x 2 = 1 a arctan x a , a > 0, 41. √<br />

− x 2 dx = x 2 a2 − x 2 + a2<br />

2 arcsin x a , a > 0,<br />

(a 2 − x 2 ) 3/2 dx = x 8 (5a2 − 2x 2 ) √ a 2 − x 2 + 3a4<br />

8 arcsin x a , a > 0,<br />

∫<br />

∫<br />

dx<br />

√<br />

a2 − x = arcsin x 2 a , a > 0, 44. dx<br />

a 2 − x 2 = 1 ∣ ∣∣∣<br />

2a ln a + x<br />

a − x∣ ,<br />

∫ √a2 √ ∣<br />

± x 2 dx = x ∣∣x<br />

2 a2 ± x 2 ± a2<br />

2 ln √ ∣ ∫<br />

∣∣<br />

+ a2 ± x 2 , 47.<br />

∫<br />

dx<br />

ax 2 + bx = 1 ∣ ∣∣∣<br />

a ln x<br />

a + bx∣ ,<br />

∫<br />

45. dx<br />

(a 2 − x 2 ) = x<br />

3/2 a 2√ a 2 − x , 2<br />

dx<br />

∣ ∣∣x<br />

√<br />

x2 − a = ln √ ∣ ∣∣ + x2 − a 2 , a > 0,<br />

2<br />

∫<br />

49. x √ 2(3bx − 2a)(a + bx)3/2<br />

a + bx dx =<br />

15b 2 ,<br />

∫ √<br />

a + bx<br />

dx = 2 √ ∫<br />

∫<br />

1<br />

a + bx + a<br />

x<br />

x √ a + bx dx,<br />

51. x<br />

√ dx = 1<br />

√ √ ∣ √ ln<br />

a + bx − a∣∣∣<br />

a + bx 2<br />

∣√ √ , a > 0,<br />

a + bx + a<br />

∫ √<br />

a2 − x 2<br />

dx = √ a<br />

x<br />

2 − x 2 a + √ a<br />

− a ln<br />

2 − x 2<br />

∫<br />

∣ x ∣ ,<br />

53. x √ a 2 − x 2 dx = − 1 3 (a2 − x 2 ) 3/2 ,<br />

∫<br />

x 2√ a 2 − x 2 dx = x 8 (2x2 − a 2 ) √ ∫<br />

∣<br />

a 2 − x 2 + a4<br />

8 arcsin x a , a > 0, 55. dx<br />

∣∣∣∣<br />

√<br />

a2 − x = − 1 2 a ln a + √ a 2 − x 2<br />

x ∣ ,<br />

∫<br />

∫<br />

x dx<br />

√<br />

a2 − x = −√ a 2 − x 2 x 2 dx<br />

, 57. √ 2 a2 − x = − √ x<br />

2 2 a2 − x 2 + a2<br />

2 arcsin x a,<br />

a > 0,<br />

∫ √<br />

a2 + x 2<br />

dx = √ a<br />

x<br />

2 + x 2 a + √ a<br />

− a ln<br />

2 + x 2<br />

∫ √ ∣ x ∣ , 59. x2 − a 2<br />

dx = √ x<br />

x<br />

2 − a 2 − a arccos a<br />

|x| , a > 0,<br />

∫<br />

x √ ∫<br />

∣ ∣<br />

x 2 ± a 2 dx = 1 3 (x2 ± a 2 ) 3/2 dx<br />

∣∣∣<br />

, 61.<br />

x √ x 2 + a = 1 2 a ln x ∣∣∣<br />

a + √ ,<br />

a 2 + x 2


Theoretical Computer Science Cheat Sheet<br />

Calculus Cont.<br />

∫<br />

∫<br />

√<br />

dx<br />

62.<br />

x √ x 2 − a = 1 2 a arccos a<br />

|x| , a > 0, 63. dx<br />

x 2√ x 2 ± a = ∓ x2 ± a 2<br />

2 a 2 ,<br />

x<br />

∫<br />

x dx<br />

64. √<br />

x2 ± a = √ ∫ √<br />

x2<br />

x 2 ± a 2 ± a<br />

, 65.<br />

2<br />

2 x 4 dx = ∓ (x2 + a 2 ) 3/2<br />

3a 2 x 3 ,<br />

∣<br />

1 ∣∣∣∣<br />

∫<br />

⎧⎪<br />

dx ⎨ √<br />

66.<br />

ax 2 + bx + c = b2 − 4ac ln 2ax + b − √ b 2 − 4ac<br />

2ax + b + √ b 2 − 4ac∣ , if b2 > 4ac,<br />

⎪ ⎩<br />

67.<br />

68.<br />

69.<br />

∫<br />

2<br />

√<br />

4ac − b<br />

2 arctan<br />

2ax + b √<br />

4ac − b<br />

2 ,<br />

if b2 < 4ac,<br />

1<br />

∣<br />

⎧⎪<br />

dx ⎨ √a ln ∣2ax + b + 2 √ a √ ax 2 + bx + c∣ , if a > 0,<br />

√<br />

ax2 + bx + c = ⎪ 1 ⎩ √ arcsin √ −2ax − b , if a < 0,<br />

−a b2 − 4ac<br />

∫ √ax2<br />

+ bx + c dx = 2ax + b √ ∫<br />

4ax − b2<br />

ax2 + bx + c +<br />

4a<br />

8a<br />

∫<br />

√<br />

x dx<br />

√<br />

ax2 + bx + c = ax2 + bx + c<br />

− b ∫<br />

a 2a<br />

dx<br />

√<br />

ax2 + bx + c ,<br />

dx<br />

√<br />

ax2 + bx + c ,<br />

−1<br />

2<br />

∫<br />

⎧⎪ √ c √ ax<br />

dx ⎨ √ ln<br />

2 + bx + c + bx + 2c<br />

, if c > 0,<br />

c<br />

70.<br />

x √ ax 2 + bx + c = ∣<br />

x<br />

∣<br />

⎪ 1<br />

bx + 2c<br />

⎩ √ arcsin −c |x| √ , if c < 0,<br />

b 2 − 4ac<br />

∫<br />

71. x 3√ x 2 + a 2 dx = ( 1 3 x2 − 2<br />

15 a2 )(x 2 + a 2 ) 3/2 ,<br />

∫<br />

∫<br />

72. x n sin(ax) dx = − 1 a xn cos(ax) + n a<br />

x n−1 cos(ax) dx,<br />

∫<br />

∫<br />

73. x n cos(ax) dx = 1 a xn sin(ax) − n a<br />

x n−1 sin(ax) dx,<br />

∫<br />

74. x n e ax dx = xn e ax ∫<br />

− n<br />

a<br />

a<br />

x n−1 e ax dx,<br />

∫<br />

( )<br />

ln(ax)<br />

75. x n ln(ax) dx = x n+1 n + 1 − 1<br />

(n + 1) 2 ,<br />

∫<br />

76. x n (ln ax) m dx = xn+1<br />

n + 1 (ln ax)m −<br />

m ∫<br />

x n (ln ax) m−1 dx.<br />

n + 1<br />

x 1 = x 1 = x 1<br />

x 2 = x 2 + x 1 = x 2 − x 1<br />

x 3 = x 3 + 3x 2 + x 1 = x 3 − 3x 2 + x 1<br />

x 4 = x 4 + 6x 3 + 7x 2 + x 1 = x 4 − 6x 3 + 7x 2 − x 1<br />

x 5 = x 5 + 15x 4 + 25x 3 + 10x 2 + x 1 = x 5 − 15x 4 + 25x 3 − 10x 2 + x 1<br />

x 1 = x 1 x 1 = x 1<br />

x 2 = x 2 + x 1 x 2 = x 2 − x 1<br />

x 3 = x 3 + 3x 2 + 2x 1 x 3 = x 3 − 3x 2 + 2x 1<br />

x 4 = x 4 + 6x 3 + 11x 2 + 6x 1 x 4 = x 4 − 6x 3 + 11x 2 − 6x 1<br />

x 5 = x 5 + 10x 4 + 35x 3 + 50x 2 + 24x 1 x 5 = x 5 − 10x 4 + 35x 3 − 50x 2 + 24x 1<br />

Finite Calculus<br />

Difference, shift operators:<br />

∆f(x) = f(x + 1) − f(x),<br />

E f(x) = f(x + 1).<br />

Fundamental Theorem:<br />

f(x) = ∆F (x) ⇔ ∑ f(x)δx = F (x) + C.<br />

b∑ ∑b−1<br />

f(x)δx = f(i).<br />

a<br />

Differences:<br />

∆(cu) = c∆u,<br />

∆(uv) = u∆v + E v∆u,<br />

∆(x n ) = nx n−1 ,<br />

i=a<br />

∆(u + v) = ∆u + ∆v,<br />

∆(H x ) = x −1 , ∆(2 x ) = 2 x ,<br />

∆(c x ) = (c − 1)c x , ∆ ( ) (<br />

x<br />

m = x<br />

m−1)<br />

.<br />

Sums:<br />

∑ ∑ cu δx = c u δx,<br />

∑ (u + v) δx =<br />

∑ u δx +<br />

∑ v δx,<br />

∑ u∆v δx = uv −<br />

∑<br />

E v∆u δx,<br />

∑ x n δx = xn+1<br />

m+1 , ∑ x −1 δx = H x ,<br />

∑ c x δx = cx<br />

c−1 , ∑ ( x<br />

) (<br />

m δx = x<br />

m+1)<br />

.<br />

Falling Factorial Powers:<br />

x n = x(x − 1) · · · (x − n + 1), n > 0,<br />

x 0 = 1,<br />

x n 1<br />

=<br />

(x + 1) · · · (x + |n|) , n < 0,<br />

x n+m = x m (x − m) n .<br />

Rising Factorial Powers:<br />

x n = x(x + 1) · · · (x + n − 1), n > 0,<br />

x 0 = 1,<br />

x n 1<br />

=<br />

(x − 1) · · · (x − |n|) , n < 0,<br />

x n+m = x m (x + m) n .<br />

Conversion:<br />

x n = (−1) n (−x) n = (x − n + 1) n<br />

= 1/(x + 1) −n ,<br />

x n = (−1) n (−x) n = (x + n − 1) n<br />

= 1/(x − 1) −n ,<br />

n∑<br />

{ } n<br />

n∑<br />

{ } n<br />

x n = x k = (−1) n−k x k ,<br />

k k<br />

x n =<br />

x n =<br />

k=1<br />

n∑<br />

k=1<br />

n∑<br />

k=1<br />

k=1<br />

[ n<br />

k<br />

]<br />

(−1) n−k x k ,<br />

[ n<br />

k<br />

]<br />

x k .


Taylor’s series:<br />

Expansions:<br />

f(x) = f(a) + (x − a)f ′ (a) +<br />

1<br />

1 − x<br />

1<br />

1 − cx<br />

Theoretical Computer Science Cheat Sheet<br />

(x − a)2<br />

f ′′ (a) + · · · =<br />

2<br />

Series<br />

∞∑ (x − a) i<br />

f (i) (a).<br />

i!<br />

i=0<br />

= 1 + x + x 2 + x 3 + x 4 + · · · =<br />

= 1 + cx + c 2 x 2 + c 3 x 3 + · · · =<br />

1<br />

1 − x n = 1 + x n + x 2n + x 3n + · · · =<br />

∞∑<br />

x i ,<br />

i=0<br />

∞∑<br />

c i x i ,<br />

i=0<br />

∞∑<br />

x ni ,<br />

x<br />

∞∑<br />

(1 − x) 2 = x + 2x 2 + 3x 3 + 4x 4 + · · · = ix i ,<br />

i=0<br />

n∑<br />

{ n k!z<br />

k<br />

∞∑<br />

k}<br />

(1 − z) k+1 = x + 2 n x 2 + 3 n x 3 + 4 n x 4 + · · · = i n x i ,<br />

k=0<br />

i=0<br />

∞∑<br />

e x = 1 + x + 1 2 x2 + 1 x i<br />

6 x3 + · · · =<br />

i! ,<br />

i=0<br />

∞∑<br />

ln(1 + x) = x − 1 2 x2 + 1 3 x3 − 1 4 x4 i+1 xi<br />

− · · · = (−1)<br />

i ,<br />

i=1<br />

1<br />

∞∑<br />

ln<br />

= x + 1<br />

1 − x<br />

2 x2 + 1 3 x3 + 1 x i<br />

4 x4 + · · · =<br />

i ,<br />

i=1<br />

∞∑<br />

sin x = x − 1 3! x3 + 1 5! x5 − 1 7! x7 + · · · = (−1) i x 2i+1<br />

(2i + 1)! ,<br />

cos x = 1 − 1 2! x2 + 1 4! x4 − 1 6! x6 + · · · =<br />

tan −1 x = x − 1 3 x3 + 1 5 x5 − 1 7 x7 + · · · =<br />

(1 + x) n = 1 + nx + n(n−1)<br />

2<br />

x 2 + · · · =<br />

1<br />

(1 − x) n+1 = 1 + (n + 1)x + ( )<br />

n+2<br />

2 x 2 + · · · =<br />

x<br />

e x − 1<br />

= 1 − 1 2 x + 1<br />

12 x2 − 1<br />

720 x4 + · · · =<br />

1<br />

2x (1 − √ 1 − 4x) = 1 + x + 2x 2 + 5x 3 + · · · =<br />

1<br />

√ 1 − 4x<br />

= 1 + 2x + 6x 2 + 20x 3 + · · · =<br />

( √<br />

1 1 − 1 − 4x<br />

√ 1 − 4x 2x<br />

1<br />

1 − x ln 1<br />

1 − x<br />

(<br />

ln<br />

1<br />

2<br />

1<br />

1 − x<br />

) n<br />

= 1 + (2 + n)x + ( )<br />

4+n<br />

2 x 2 + · · · =<br />

= x + 3 2 x2 + 11<br />

6 x3 + 25<br />

12 x4 + · · · =<br />

) 2<br />

= 1 2 x2 + 3 4 x3 + 11<br />

24 x4 + · · · =<br />

x<br />

1 − x − x 2 = x + x 2 + 2x 3 + 3x 4 + · · · =<br />

F n x<br />

1 − (F n−1 + F n+1 )x − (−1) n x 2 = F n x + F 2n x 2 + F 3n x 3 + · · · =<br />

i=0<br />

i=0<br />

∞∑<br />

i=0<br />

(−1) i x2i<br />

(2i)! ,<br />

∞∑<br />

(−1) i x 2i+1<br />

(2i + 1) ,<br />

∞∑<br />

( ) n<br />

x i ,<br />

i<br />

i=0<br />

i=0<br />

∞∑<br />

( i + n<br />

i<br />

i=0<br />

∞∑ B i x i<br />

,<br />

i!<br />

i=0<br />

∞∑<br />

(<br />

1 2i<br />

i + 1 i<br />

i=0<br />

∞∑<br />

( ) 2i<br />

x i ,<br />

i<br />

i=0<br />

∞∑<br />

( 2i + n<br />

i<br />

∞∑<br />

H i x i ,<br />

i=0<br />

i=1<br />

∞∑ H i−1 x i<br />

,<br />

i<br />

∞∑<br />

F i x i ,<br />

i=2<br />

i=0<br />

∞∑<br />

F ni x i .<br />

i=0<br />

)<br />

x i ,<br />

)<br />

x i ,<br />

)<br />

x i ,<br />

Ordinary power series:<br />

∞∑<br />

A(x) = a i x i .<br />

i=0<br />

Exponential power series:<br />

∞∑ x i<br />

A(x) = a i<br />

i! .<br />

i=0<br />

Dirichlet power series:<br />

∞∑ a i<br />

A(x) =<br />

i x .<br />

i=1<br />

Binomial theorem:<br />

n∑<br />

( n<br />

(x + y) n = x<br />

k)<br />

n−k y k .<br />

k=0<br />

Difference of like powers:<br />

n−1<br />

∑<br />

x n − y n = (x − y) x n−1−k y k .<br />

k=0<br />

For ordinary power series:<br />

∞∑<br />

αA(x) + βB(x) = (αa i + βb i )x i ,<br />

x k A(x) =<br />

i=0<br />

∞∑<br />

a i−k x i ,<br />

i=k<br />

A(x) − ∑ k−1<br />

i=0 a ix i<br />

x k =<br />

∫<br />

A(cx) =<br />

A ′ (x) =<br />

xA ′ (x) =<br />

A(x) dx =<br />

A(x) + A(−x)<br />

2<br />

A(x) − A(−x)<br />

2<br />

=<br />

=<br />

∞∑<br />

a i+k x i ,<br />

i=0<br />

∞∑<br />

c i a i x i ,<br />

i=0<br />

∞∑<br />

(i + 1)a i+1 x i ,<br />

i=0<br />

∞∑<br />

ia i x i ,<br />

i=1<br />

∞∑<br />

i=1<br />

a i−1<br />

x i ,<br />

i<br />

∞∑<br />

a 2i x 2i ,<br />

i=0<br />

∞∑<br />

a 2i+1 x 2i+1 .<br />

i=0<br />

Summation: If b i = ∑ i<br />

j=0 a i then<br />

B(x) = 1<br />

1 − x A(x).<br />

Convolution:<br />

⎛ ⎞<br />

∞∑ i∑<br />

A(x)B(x) = ⎝ a j b i−j<br />

⎠ x i .<br />

i=0<br />

j=0<br />

God made the natural numbers;<br />

all the rest is the work of man.<br />

– Leopold Kronecker


Theoretical Computer Science Cheat Sheet<br />

Series<br />

Expansions:<br />

1<br />

(1 − x) n+1 ln 1<br />

∞∑<br />

( ) ( ) −n n + i<br />

1<br />

= (H n+i − H n ) x i ,<br />

=<br />

1 − x<br />

i<br />

x<br />

i=0<br />

∞∑<br />

[ ] n<br />

x n = x i , (e x − 1) n =<br />

i<br />

∞∑<br />

i=0<br />

{ i<br />

n}<br />

x i ,<br />

∞∑<br />

{ i n!x<br />

i<br />

,<br />

n}<br />

i!<br />

i=0<br />

i=0<br />

( ) n<br />

1<br />

∞∑<br />

[ i n!x<br />

i<br />

∞∑ (−4)<br />

ln<br />

=<br />

, x cot x =<br />

1 − x<br />

n] i B 2i x 2i<br />

,<br />

i!<br />

(2i)!<br />

i=0<br />

i=0<br />

∞∑<br />

tan x = (−1) i−1 22i (2 2i − 1)B 2i x 2i−1<br />

∞∑ 1<br />

, ζ(x) =<br />

(2i)!<br />

i x ,<br />

i=1<br />

i=1<br />

1<br />

∞∑ µ(i)<br />

=<br />

ζ(x)<br />

i x , ζ(x − 1)<br />

∞∑<br />

=<br />

ζ(x)<br />

i=1<br />

ζ(x) = ∏ p<br />

∞∑<br />

ζ 2 (x) =<br />

ζ(x)ζ(x − 1) =<br />

i=1<br />

∞∑<br />

i=1<br />

1<br />

1 − p −x ,<br />

d(i)<br />

x i where d(n) = ∑ d|n 1,<br />

S(i)<br />

x i where S(n) = ∑ d|n d,<br />

ζ(2n) = 22n−1 |B 2n |<br />

π 2n , n ∈ N,<br />

(2n)!<br />

x<br />

∞∑<br />

= (−1) i−1 (4i − 2)B 2i x 2i<br />

,<br />

sin x<br />

(2i)!<br />

2x<br />

i=0<br />

( √ ) n<br />

1 − 1 − 4x<br />

∞∑<br />

=<br />

e x sin x =<br />

√<br />

1 − √ 1 − x<br />

=<br />

x<br />

( ) 2 arcsin x<br />

=<br />

x<br />

i=0<br />

∞∑<br />

i=1<br />

∞∑<br />

i=0<br />

∞∑<br />

i=0<br />

n(2i + n − 1)!<br />

x i ,<br />

i!(n + i)!<br />

2 i/2 sin iπ 4<br />

i!<br />

x i ,<br />

(4i)!<br />

16 i√ 2(2i)!(2i + 1)! xi ,<br />

4 i i! 2<br />

(i + 1)(2i + 1)! x2i .<br />

Cramer’s Rule<br />

If we have equations:<br />

a 1,1 x 1 + a 1,2 x 2 + · · · + a 1,n x n = b 1<br />

i=1<br />

ϕ(i)<br />

i x , Stieltjes Integration<br />

Escher’s Knot<br />

If G is continuous in the interval [a, b] and F is nondecreasing then<br />

exists. If a ≤ b ≤ c then<br />

∫ c<br />

a<br />

G(x) dF (x) =<br />

∫ b<br />

a<br />

∫ b<br />

a<br />

G(x) dF (x)<br />

G(x) dF (x) +<br />

∫ c<br />

If the integrals involved exist<br />

∫ b<br />

∫<br />

( ) b<br />

G(x) + H(x) dF (x) = G(x) dF (x) +<br />

a<br />

∫ b<br />

a<br />

∫ b<br />

a<br />

∫ b<br />

G(x) d ( F (x) + H(x) ) =<br />

a<br />

c · G(x) dF (x) =<br />

∫ b<br />

a<br />

a<br />

∫ b<br />

a<br />

b<br />

G(x) dF (x) +<br />

G(x) d ( c · F (x) ) = c<br />

G(x) dF (x) = G(b)F (b) − G(a)F (a) −<br />

G(x) dF (x).<br />

∫ b<br />

a<br />

∫ b<br />

a<br />

∫ b<br />

a<br />

∫ b<br />

a<br />

H(x) dF (x),<br />

G(x) dH(x),<br />

G(x) dF (x),<br />

F (x) dG(x).<br />

If the integrals involved exist, and F possesses a derivative F ′ at every<br />

point in [a, b] then<br />

∫ b<br />

∫ b<br />

G(x) dF (x) = G(x)F ′ (x) dx.<br />

00 47 18 76 29 93 85 34 61 52<br />

13, 21, 34, 55, 89, . . .<br />

86 11 57 28 70 39 94 45 02 63<br />

det A . Additive rule:<br />

95 80 22 67 38 71 49 56 13 04<br />

59 96 81 33 07 48 72 60 24 15<br />

1, 1, 2, 3, 5, 8,<br />

Definitions:<br />

73 69 90 82 44 17 58 01 35 26 F i = F i−1 +F i−2 , F 0 = F 1 = 1,<br />

.<br />

68 74 09 91 83 55 27 12 46 30<br />

F −i = (−1) i−1 F i ,<br />

37 08 75 19 92 84 66 23 50 41<br />

F<br />

14 25 36 40 51 62 03 77 88 99<br />

i = √ 1 5<br />

(ϕ i − ˆϕ i) ,<br />

21 32 43 54 65 06 10 89 97 78 Cassini’s identity: for i > 0:<br />

42 53 64 05 16 20 31 98 79 87<br />

F i+1 F i−1 − Fi 2 = (−1) i .<br />

a 2,1 x 1 + a 2,2 x 2 + · · · + a 2,n x n = b 2<br />

. .<br />

a n,1 x 1 + a n,2 x 2 + · · · + a n,n x n = b n<br />

Let A = (a i,j ) and B be the column matrix (b i ). Then<br />

there is a unique solution iff det A ≠ 0. Let A i be A<br />

with column i replaced by B. Then<br />

x i = det A i<br />

Improvement makes strait roads, but the crooked<br />

roads without Improvement, are roads of Genius.<br />

– William Blake (The Marriage of Heaven and Hell)<br />

The Fibonacci number system:<br />

Every integer n has a unique<br />

representation<br />

n = F k1 + F k2 + · · · + F km ,<br />

where k i ≥ k i+1 + 2 for all i,<br />

1 ≤ i < m and k m ≥ 2.<br />

a<br />

a<br />

Fibonacci Numbers<br />

F n+k = F k F n+1 + F k−1 F n ,<br />

F 2n = F n F n+1 + F n−1 F n .<br />

Calculation by matrices:<br />

( ) ( ) n<br />

Fn−2 F n−1 0 1<br />

= .<br />

F n−1 F n 1 1

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