Lecture Notes in Differential Equations - Bruce E. Shapiro

Lecture Notes in Differential Equations - Bruce E. Shapiro Lecture Notes in Differential Equations - Bruce E. Shapiro

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416 APPENDIX C. SUMMARY OF METHODS To solve a(t)y ′′ + b(t)y ′ + c(t)y = g(t) about a point t 0 where a(t) = 0 but the limits b(t)/a(t) and c(t)/a(t) exist as t → 0 (a regular singularity), solve the indicial equation r(r − 1) + rp 0 + q 0 = 0 for r where p 0 = lim t→0 b(t 0 )/a(t 0 ) and and q 0 = lim t→0 c(t 0 )/a(t 0 ). Then one solution to the homogeneous equation is y(t) = (t − t 0 ) r ∞ ∑ k=0 c k (t − t 0 ) k for some unknown coefficients c k .Determine the coefficients by linear independance of the powers of t. The second solution is found by reduction of order and the particular solution by variation of parameters. Method of Frobenius To solve (t − t 0 ) 2 y ′′ + (t − t 0 )p(t)y ′ + q(t)y = 0 where p and q are analytic at t 0 , let p 0 = p(0) and q 0 = q(0) and find the roots α 1 ≥ α 2 of α 2 + (p 0 − 1)α + q 0 = 0 Define ∆ = α 1 − α 2 . Then for some unknowns c k , a first solution is y 1 (t) = (t − t 0 ) α1 ∞ ∑ k=0 c k (t − t 0 ) k If ∆ ∈ R is not an integer or the roots are complex, y 2 (t) = (t − t 0 ) α2 ∞ ∑ k=0 a k (t − t 0 ) k If α 1 = α 2 = α, then y 2 = ay 1 (t) ln |t − t 0 | + (t − t 0 ) α If ∆ ∈ Z, then y 2 = ay 1 (t) ln |t − t 0 | + (t − t 0 ) α2 ∞ ∑ k=0 ∞ ∑ k=0 a k (t − t 0 ) k a k (t − t 0 ) k

Bibliography [1] Bear, H.S. Differential Equations. Addison-Wesley. (1962) Has a very good description of Picard iteration that many students find helpful. Unfortunately this text is long since out of print so you’ll have to track it down in the library. [2] Boyce, William E and DiPrima, Richard C. Elementary Differential Equations. 9th Edition. Wiley. (2008) This is the classic introductory textbook on differential equations. It also has a longer version with two additional chapters that cover boundary value problems but is otherwise identical. It is at the same level as [12] and [9] and the choice of which book you read really depends on your style. The first edition of this book was the best; the later editions have only served to fill the coffers of the publishers, while the later editions use heavy paper and are quite expensive. Each edition just gets heavier and heavier. [3] Bronson, Richard and Costa Gabriel. Schaum’s Outline of Differential Equations. 4th Edition. McGraw-Hill. (2006) The usual from Schaum’s. A good, concise, low cost outline of the subject. [4] Churchill, Ruel V. Operational Mathematics. 3rd Edition McGraw-Hill. (1972) Classic textbook on Laplace and Fourier methods. [5] Coddington, Earl A. An Introduction to Ordinary Differential Equations. Dover Books (1989). This is a reprint of an earlier edition. It contains the classical theory of differential equations with all of the proofs at a level accessible to advanced undergraduates with a good background in calculus. (Analysis is not a prerequisite to this textbook). Lots of bang for your buck. [6] Coddington, Earl A. Levinson, Norman. Theory of Ordinary Differential Equations. Krieger (1984) (Reprint of earlier edition). The standard graduate text in classical differential equations written in the 417

Bibliography<br />

[1] Bear, H.S. <strong>Differential</strong> <strong>Equations</strong>. Addison-Wesley. (1962) Has a very<br />

good description of Picard iteration that many students f<strong>in</strong>d helpful.<br />

Unfortunately this text is long s<strong>in</strong>ce out of pr<strong>in</strong>t so you’ll have to track<br />

it down <strong>in</strong> the library.<br />

[2] Boyce, William E and DiPrima, Richard C. Elementary <strong>Differential</strong><br />

<strong>Equations</strong>. 9th Edition. Wiley. (2008) This is the classic <strong>in</strong>troductory<br />

textbook on differential equations. It also has a longer version with<br />

two additional chapters that cover boundary value problems but is<br />

otherwise identical. It is at the same level as [12] and [9] and the choice<br />

of which book you read really depends on your style. The first edition<br />

of this book was the best; the later editions have only served to fill the<br />

coffers of the publishers, while the later editions use heavy paper and<br />

are quite expensive. Each edition just gets heavier and heavier.<br />

[3] Bronson, Richard and Costa Gabriel. Schaum’s Outl<strong>in</strong>e of <strong>Differential</strong><br />

<strong>Equations</strong>. 4th Edition. McGraw-Hill. (2006) The usual from Schaum’s.<br />

A good, concise, low cost outl<strong>in</strong>e of the subject.<br />

[4] Churchill, Ruel V. Operational Mathematics. 3rd Edition McGraw-Hill.<br />

(1972) Classic textbook on Laplace and Fourier methods.<br />

[5] Codd<strong>in</strong>gton, Earl A. An Introduction to Ord<strong>in</strong>ary <strong>Differential</strong> <strong>Equations</strong>.<br />

Dover Books (1989). This is a repr<strong>in</strong>t of an earlier edition. It<br />

conta<strong>in</strong>s the classical theory of differential equations with all of the<br />

proofs at a level accessible to advanced undergraduates with a good<br />

background <strong>in</strong> calculus. (Analysis is not a prerequisite to this textbook).<br />

Lots of bang for your buck.<br />

[6] Codd<strong>in</strong>gton, Earl A. Lev<strong>in</strong>son, Norman. Theory of Ord<strong>in</strong>ary <strong>Differential</strong><br />

<strong>Equations</strong>. Krieger (1984) (Repr<strong>in</strong>t of earlier edition). The standard<br />

graduate text <strong>in</strong> classical differential equations written <strong>in</strong> the<br />

417

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