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8.12. ∫ sin( ax + b)<br />
dx ; 8.13.<br />
∫<br />
dx<br />
5x<br />
4<br />
+ ; 8.14. ∫ ( α− ) 8<br />
5 dα;<br />
dv<br />
8.15. ∫<br />
2<br />
v + 7<br />
; 8.16. 3dt<br />
dx<br />
∫ 2 ; 8.17. ∫<br />
5 t<br />
3<br />
(3x<br />
+ 2)<br />
;<br />
8.18.<br />
8.21.<br />
8.24.<br />
8.27.<br />
∫<br />
∫<br />
dx<br />
2x<br />
+ 5<br />
; 8.19. ∫ ctg 5xdx ; 8.20.<br />
cos xdx<br />
2sin x + 1<br />
; 8.22. sin 2xdx<br />
∫ ; 8.23.<br />
2<br />
1+<br />
sin x<br />
x<br />
edx<br />
∫<br />
3+<br />
4e<br />
∫<br />
x<br />
x<br />
3<br />
xdx<br />
4 4<br />
+ a<br />
; 8.25.<br />
; 8.28.<br />
∫<br />
∫<br />
xdx<br />
9 − x<br />
2<br />
xdx<br />
bx − a<br />
2 2 2<br />
; 8.26.<br />
; 8.29.<br />
2<br />
x<br />
∫ xsin dx ; 3<br />
∫<br />
∫<br />
∫<br />
cos 2xdx<br />
( 2+<br />
sin2x) 3<br />
xdx<br />
x + ;<br />
2<br />
2 3<br />
a<br />
− x dx .<br />
2 2<br />
8.3.3. Ìåòîä ³íòåãðóâàííÿ ÷àñòèíàìè<br />
Íåõàé çàäàí³ äâ³ äèôåðåíö³éîâí³ ôóíêö³¿: u = u(x) ³<br />
v = v(x). Ðîçãëÿíåìî äîáóòîê y = uv. Çíàéäåìî<br />
dy = udv + vdu àáî d(uv) =udv + vdu. Óçÿâøè â³ä îáîõ ÷àñòèí<br />
îñòàííüî¿ ð³âíîñò³ ³íòåãðàë, îòðèìàºìî<br />
àáî<br />
∫duv ( ) = ∫udv + ∫ vdu,<br />
uv = ∫udv + ∫vdu ⇒ ∫udv = uv −∫ vdu . (8.3.10)<br />
Öÿ ôîðìóëà íàçèâàºòüñÿ ôîðìóëîþ ³íòåãðóâàííÿ ÷àñòèíàìè.<br />
Âîíà âèêîðèñòîâóºòüñÿ åôåêòèâíî òîä³, êîëè ³íòåãðàë<br />
ó ïðàâ³é ÷àñòèí³ ñïðîùóºòüñÿ ó ñåíñ³ ³íòåãðóâàííÿ.<br />
Íàïðèêëàä,<br />
x<br />
x<br />
⎡ x= u,<br />
dv=<br />
e dx⎤<br />
x x x x<br />
∫xe dx = ⎢<br />
xe e dx xe e C<br />
x ⎥ = − ∫ = − + .<br />
⎣du = dx,<br />
v = e ⎦<br />
;<br />
Çà äîïîìîãîþ ìåòîäà ³íòåãðóâàííÿ ÷àñòèíàìè çíàõîäÿòüñÿ<br />
³íòåãðàëè âèäó:<br />
1. ∫ P ( ) x<br />
n<br />
x e dx , äå P n (x) — ìíîãî÷ëåí n-ãî ñòåïåíÿ. Ôîðìóëà<br />
³íòåãðóâàííÿ ÷àñòèíàìè â öüîìó âèïàäêó çàñòîñîâóºòüñÿ<br />
ïîñë³äîâíî:<br />
x<br />
Px ( ) = u, i= n, n− 1, K ,1, edx=<br />
dv.<br />
i<br />
2. ( ) ax +<br />
∫ P b<br />
n<br />
x e dx , ∫ Pn<br />
( x)sinxdx<br />
, ∫ Pn<br />
( x)cosxdx<br />
, ∫ Pn<br />
( x)sin( ax+<br />
b)<br />
dx ,<br />
∫ Pn<br />
( x)cos( ax+<br />
b)<br />
dx .<br />
×åðåç u ïîçíà÷àþòü P n (x), à ÷åðåç dv — âèðàç, ùî çàëèøèâñÿ<br />
ï³ä çíàêîì ³íòåãðàëà.<br />
Íàïðèêëàä,<br />
2<br />
2<br />
⎡ x = u dv = sin xdx⎤<br />
2<br />
∫x sin xdx = ⎢<br />
⎥ = − x cos x + 2∫xcos<br />
xdx =<br />
⎣du = 2xdx v = −cosx<br />
⎦<br />
⎡ x = u dv = cos xdx⎤<br />
= ⎢<br />
= − cos + 2 sin + 2 cos +<br />
du = dx v = sin x<br />
⎥<br />
⎣<br />
⎦<br />
2<br />
x x x x x C<br />
3. ∫ Pn<br />
( x)lnxdx<br />
. Òóò ñë³ä ïîêëàñòè ln x = u, P n (x)dx = dv.<br />
4. ∫ P ( )ln m<br />
n<br />
x xdx , äå m — ö³ëå äîäàòíå ÷èñëî, m > 1. ²íòåãðóºòüñÿ<br />
øëÿõîì ïîñë³äîâíîãî çàñòîñóâàííÿ ôîðìóëè ³íòåãðóâàííÿ<br />
÷àñòèíàìè:<br />
i<br />
ln x = u, i = m, m − 1, K ,1, Pn<br />
( x)<br />
dx = dv.<br />
Íàïðèêëàä,<br />
2<br />
⎡ ln x= u dv=<br />
xdx⎤<br />
2 2<br />
2 x<br />
2<br />
2 x 1<br />
xln xdx<br />
⎢<br />
⎥<br />
∫ = 1 x = ln x− 2lnx dx=<br />
⎢<br />
∫<br />
du = 2lnx dx v =<br />
⎥ 2 2 x<br />
⎢⎣<br />
x 2 ⎥⎦<br />
2<br />
⎡lnx= u dv=<br />
xdx⎤<br />
2 2 2<br />
x 2 x 2<br />
2 x x<br />
= ln x− xlnxdx ⎢<br />
⎥<br />
∫ = dx x = ln x− lnx+ + C<br />
2 ⎢du<br />
v ⎥<br />
.<br />
= = 2 2 4<br />
⎢⎣<br />
x 2 ⎥⎦<br />
.<br />
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