Integrallash
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bo'laklab integrallash
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- Kasr ratsional funksiya
- Tarif.
- 3. Sodda ratsional kasrlarni integrallash.
M A’RUZA 9 4.9. BO’LAKLAB INTEGRALLASH. RATSIONAL KASRLARNI SODDA KASRLARGA YOYIB INTEGRALLASH. TRIGONOMETRIK FUNKSIYALARNI INTEGRALLASH. Reja. 1. Bo’laklab integrallash 2. Kasr ratsional funksiya 3. Sodda ratsional kasrlarni integrallash. 4. Kasr ratsional funksiyalarni sodda kasrlarga keltirish. 5.
R(sinx,cosx)dx ko’rinishdagi integrallarni integrallash. 6. J =
7. J = R(tgx)dx ko’rinishdagi integrallarni integrallash 8. xdx x J n m cos
sin ko’rinishdagi integrallarni integrallash
9.
cosmx
cosnxdx; sinmx
cosnxdx; sinmx
sinnxdx (m n) ko’rinishidagi integrallarni integrallash Tayanch so’zlar. Ko’phad, ratsional kasr, to’g’ri va noto’g’ri kasr, ko;phad ildizlari,karrali ildiz 1. Bo’laklab integrallash. Agar x bo’yicha differensiallanuvchi bo’lgan u(x) , v(x) funksiyalar berilgan bo’lsa, u holda uv ko’paytmaning differensiali quyidagi formula bilan hisoblanar edi :
d(uv)=udv+vdu (3) (3) ning har ikkala tomonini integrallasak:
∫d(uv) = ∫udv + ∫vdu ∫udv = uv-∫vdu (4)
(4) formulaga bo’laklab integrallash formulasi deyiladi. (4) formula ∫vdu integralni hisoblash ∫udv integralni hisoblashdan osonroq bo’lgan holda foydalaniladi.
Bo’aklab integrallash usuli bilan hisoblanadigan ayrim integrallarni ko’rib o’taylik. I. ∫P(x)e kx
dx , ∫p(x)sinkx dx , ∫P(x)coskxdx, (P(x) - ko’phad, k esa biror o’zgarmas son) ko’rinishdagi integrallarni bo’laklab integrallaganda u=P(x), qolganlarini dv deb olish maqsadga muvofiq bo’ladi.
integrallarni integrallaganda u deb lnx, arcsinx, arccosx, arctgx, arcctgx larni olish kerak.
III. ∫e ax sinb x dx∫e
ax cosbxdx, ko’rinishdagi integrallar ikki martabo’laklab integrallanadi. 1-misol. ∫xe x dx = C e xe dx e xe e v dx, e dv dx du x, u x x x x x x
C x
1 1nx
x 9 1 x dx 3 x 1nx
3 x 1nx 3 x 3 x v dx, x dv x dx du 1nx, u 1nxdx
x 3 3 3 3 3 3 2 2 3-misol. J=∫e x cosxdx= sinxdx e sinx e sinx
v cosxdx,
dv dx e du , e u x x x x
cosxdx e cosx
e cosx
v dx,
sinx dv dx e du , e u sinxdx e x x x x x
C cosx)
(sinx e cosxdx e 2 cosxdx e - cosx e sinx
e cosxdx
e x x x x x x C cosx) (sinx e 2 1 cosxdx
e x x
2. Kasr ratsional funksiya Ma'lumki P n (x) a
0 x n +a 1 x n-1 +...+a
n-1 x+a
n (a 0 ≠0) (1)ko’phad butun ratsional funksiya deyiladi.
0) b 0, (a b x b ... x b x b a x a ... x a x a (x)
Q (X)
P 0 0 m 1 m 1 m 1 m 0 n 1 n 1 n 1 n 0 m n esa kasr ratsional funksiya deyiladi.
Butun va kasr ratsional funksiyalar umuman ratsional funksiyalar deb ataladi. Butun ratsional funksiyalarni integrallash integralning asosiy xossalariga ko’ra bajariladi.
∫ P
n (x) dx = ∫ (a o x
+a 1 x n-1 +...+a
n-1 x+a
n )dx =
C x a x 1 n a ...
x n a x 1 n a n 2 1 n n 1 1 n 0 Agar (2) kasr ratsional funksiya berilgan bo’lib n bo’lsa (2) ga noto’g’ri kasr deyiladi.
Agar kasr noto’g’ri bo’lsa, suratini maxrajiga bo’lib, berilgan kasrni biror butun ratsional funksiya bilan biror to’g’ri kasrning yig’indisi ko’rinishda ifodalash mumkin, ya'ni (x)
Q (X)
P m n =M(x)+ (x)
Q (X)
P m k , bu yerda M(x) - butun ratsional funksiya, (x)
Q (X)
P m k - to’g’ri kasr chunki k Ko’phadlarni integrallash hech qanday qiyinchilik tug’dirmaydi, shuning uchun biz asosan to’g’ri
ratsional kasrlarni integrallash bilan shug’ullanamiz.
,...)
3
( a) (x A II. ; a x A n
III. 0 q 4 p D 2,3,...;
n q) px (x B Ax IV. 0 q 4 p D q px x B Ax 2 n 2 2 2
Bu yerda A,B,a,p,q lar haqiqiy sonlar q px x 2 kvadrat uchhad haqiqiy ildizga ega emas, ya'ni D<0 deb qaraladi
Endi yuqoridagi to’rtta eng sodda ratsional kasrlarni integrallashni ko’raylik. I. ∫ C | a x | A1n a x a) d(x
A a x dx A
C n)
(1 A a) d(x a) (x A a) (x dx A 1 n n n
III. q px x dx Ap B dx p x dx 2 2 2 2 ) 2 ( q px x 2 2 A q px x B 2 Ap p) (2x 2 A dx q px x B Ax Oxirgi tenglikning o’ng tomonidagj birinchi integral ln|x 2 tengligi ravshan, chunki surati maxrajining hosilasiga teng.
Ikkinchi integralda esa, quyidagi almashtirishlar bajaramiz. C p q p x arctg p q Ap B q px x n C k t arctg Ap B k q px x n k t dx Ap B q px x d dx q px x B Ax 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 4 2 4 2 | | 1 2 A 2 1 | | 1 2 A ) 2 ( ) q px x ( 2 A k t k 4 p q dt dx desak t 2 p x 4 p q 2 p x q px x
1. C 12x x 2 7 4x x 4 5 12)dx
7x 4x (5x 2 3 4 2 3
2. C 3) 4(x 7dx C 3) (x 4 7 dx 3) (x 7 3) (x 7dx 4 4 5 5
3. C | 13 6x x | 1n 13 6x x 13) 6x d(x
dx 13 6x x 6 2x 2 2 2 2
4. C 3 4 x arctg 3 11 9 4) (x 4) dx(x 11 9 4) (x dx 11 25 8x x 11dx
2 2 2 Agar maxrajdagi kvadrat uchhadning diskriminanti musbat bo’lsa, ya'ni kvadrat uchhad haqiqiy ildizga ega bo’lsa integrallar jadvalidagi natural logarifmni beradi. 5.
C 1 x 5 x 1n 4 1 C 2 3 x 3 3 x 1n 2 2 1 4 3) (x dx 5 6x x dx 2 2
VI. n 2 n 2 n 2 n 2 q) px (x ) 2 ( q) px (x ) 2 ( 2 A q) px (x ) 2 Ap ( p) (2x
2 A dx q) px (x B Ax dx Ap B dx dx p x dx B
O’ng tomonidagi birinchi integralni integrallasak C q) px n)(x (1 1 C 1 n t t dt dt p)dx
(2x t q px x q) px (x p)dx (2x 1 n 2 1 n n 2 n 2
Ikkinchi integralni esa J n deb belgilasak:
n n n n n n k t dt t J k k t dt t k k t dt k k t t k t k k t dt k p q t p x p q p x dx dx ) ( 1 ) ( 1 ) ( 1 ) ( 1 ) ( 4 , 2 4 2 q) px (x J 2 2 2 1 2 2 2 2 2 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 n 2 n
Oxirgi integralni bo’laklab integrallasak
; ) ( ; ) ( 2 2 2 2 2 n n k t tdt dv dt du t u k t dt t 1 2 2 2 2 2 2 ) )( 1 ( 2 1 2 1 2 ) ( n n n k t n z dz dz tdt z k t k t tdt v = 1 ) 1 ( 2 1 ) )( 1 ( 2 ) ( ) 1 ( 2 1 ) )( 1 ( 2 1 2 2 1 2 2 1 2 2 n J n k t n t k t dt n k t n t n n n
J n= 1 2 2 1 1 2 ) )( 1 ( 2 ) 1 ( 2 1 1 n n n k t n t J n J k
1 1 2 2 2 2 2 2 2 3 2 ) )( 2 2 ( 1 1 ) (
n n n J n n k t n k k t dt J
(n 1)
Bunga rekkurent (keltirish ) formulasi deyiladi. Shu jarayonni n marta davom ettirsak c k t arctg k k t dt J 1 ) ( 2 2 1 ga kelamiz. Misol.
dx t x x dx x x dx x dx x x x x x dx x J 1 1 ) 1 ( 2 ) 2 2 ( ) 2 2 ( 2 3 ) 2 2 ( 5 3 ) 2 2 ( 2 3 ) 2 2 ( ) 5 3 ( 2 2 2 2 2 2 2
; ) 1 ( 2 ) 2 2 ( 2 3 2 2 2 t dt x x
1 1 , ) 1 ( 2 , ) 1 ( 2 2 1 1 ) 1 ( ) 1 ( ) 1 ( 2 2 2 2 2 2 2 2 2 2 2 2 2
v t tdt dv dt du t u t tdt t t dt t dt t t t dt J
=arctgt C arctgt t t C arctgt t acrtgt t dt t t 2 1 ) 1 ( 2 2 1 ) 1 ( 2 1 ) 1 1 ( 2 1 2 2 2 2 J 2 C x arctg x x x x x J C x arctg x x x ) 1 ( 2 2 1 ) 2 2 ( 2 3
) 1 ( 2 1 ) 2 2 ( 2 1 2 2 2
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