这个谁会,要详解
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解决时间 2021-01-27 08:24
- 提问者网友:斑駁影
- 2021-01-27 01:14
这个谁会,要详解
最佳答案
- 五星知识达人网友:神的生死簿
- 2021-01-27 02:22
xarcsin√x-∫xd(arcsin√x)可能对后面的式子还要分部追答(方法一)直接采用换元积分法
设 t=arcsin√x则
sint=√x,cost=√(1-x),x=sin²t,dx=2sintcostdt=sin2tdt
于是
∫arcsin√xdx
=∫tsin2tdt
=∫(-1/2)tdcos2t
=(-1/2)tcos2t+∫(1/2)cos2tdt
=(-1/2)tcos2t+(1/4)sin2t+C
=(-1/2)t(1-2sin²t)+(1/2)sintcost+C
=(-1/2)(1-2x)arcsin√x+(1/2)√x(1-x)+C
=(1/2)[√x(1-x)-(1-2x)arcsin√x]+C
(方法二)先分部积分
∫arcsin√xdx
=xarcsin√x-∫xdarcsin√x
=xarcsin√x-∫xdarcsin√x
=xarcsin√x-∫(1/2)√[x/(1-x)]dx
再换元
令√[x/(1-x)]=t,则
x/(1-x)=t²,x=t²-xt²,x(1+t²)=t²,x=t²/(1+t²) dx={[2t(1+t²)-t²×2t]/(1+t²)²}dt=[2t/(1+t²)²]dt于是
∫√[x/(1-x)]dx
=∫t[2t/(1+t²)²]dt=2∫[(1+t²-1)/(1+t²)²]dt=2∫[1/(1+t²)]dt-∫[1/(1+t²)²]dt=2arctant-∫[1/(1+t²)²]dt。再换元
令t=tanu,则 u=arctant,dt=sec²udu于是
∫√[x/(1-x)]dx
=2arctant-∫{1/[1+(tanu)^2]^2}(secu)^2du=2arctan√[x/(x-1)]+∫(cosu)^4(secu)^2du=2arctan√[x/(x-1)]+∫(cosu)^2du=2arctan√[x/(x-1)]+(1/2∫(1+cos2u)du=2arctan√[x/(x-1)]+(1/2)∫du+(1/4)∫cos2ud(2u)=2arctan√[x/(x-1)]+(1/2)u+(1/4)sin2u+C=2arctan√[x/(x-1)]+(1/2)arctant+(1/4)sin2arctant+C=2arctan√[x/(x-1)]+(1/2)arctan√[x/(x-1)]+(1/4)sin2arctan√[x/(x-1)]+C=(5/2)arctan√[x/(x-1)]+(1/4)sin2arctan√[x/(x-1)]+C1
从而
∫arcsin√xdx
=xarcsin√x-(5/4)arctan√[x/(x-1)]-(1/8)sin2arctan√[x/(x-1)]+C自己想分部还是很重要的
设 t=arcsin√x则
sint=√x,cost=√(1-x),x=sin²t,dx=2sintcostdt=sin2tdt
于是
∫arcsin√xdx
=∫tsin2tdt
=∫(-1/2)tdcos2t
=(-1/2)tcos2t+∫(1/2)cos2tdt
=(-1/2)tcos2t+(1/4)sin2t+C
=(-1/2)t(1-2sin²t)+(1/2)sintcost+C
=(-1/2)(1-2x)arcsin√x+(1/2)√x(1-x)+C
=(1/2)[√x(1-x)-(1-2x)arcsin√x]+C
(方法二)先分部积分
∫arcsin√xdx
=xarcsin√x-∫xdarcsin√x
=xarcsin√x-∫xdarcsin√x
=xarcsin√x-∫(1/2)√[x/(1-x)]dx
再换元
令√[x/(1-x)]=t,则
x/(1-x)=t²,x=t²-xt²,x(1+t²)=t²,x=t²/(1+t²) dx={[2t(1+t²)-t²×2t]/(1+t²)²}dt=[2t/(1+t²)²]dt于是
∫√[x/(1-x)]dx
=∫t[2t/(1+t²)²]dt=2∫[(1+t²-1)/(1+t²)²]dt=2∫[1/(1+t²)]dt-∫[1/(1+t²)²]dt=2arctant-∫[1/(1+t²)²]dt。再换元
令t=tanu,则 u=arctant,dt=sec²udu于是
∫√[x/(1-x)]dx
=2arctant-∫{1/[1+(tanu)^2]^2}(secu)^2du=2arctan√[x/(x-1)]+∫(cosu)^4(secu)^2du=2arctan√[x/(x-1)]+∫(cosu)^2du=2arctan√[x/(x-1)]+(1/2∫(1+cos2u)du=2arctan√[x/(x-1)]+(1/2)∫du+(1/4)∫cos2ud(2u)=2arctan√[x/(x-1)]+(1/2)u+(1/4)sin2u+C=2arctan√[x/(x-1)]+(1/2)arctant+(1/4)sin2arctant+C=2arctan√[x/(x-1)]+(1/2)arctan√[x/(x-1)]+(1/4)sin2arctan√[x/(x-1)]+C=(5/2)arctan√[x/(x-1)]+(1/4)sin2arctan√[x/(x-1)]+C1
从而
∫arcsin√xdx
=xarcsin√x-(5/4)arctan√[x/(x-1)]-(1/8)sin2arctan√[x/(x-1)]+C自己想分部还是很重要的
全部回答
- 1楼网友:胯下狙击手
- 2021-01-27 03:27
分部积分,被窝里,不好给详解,自己做最好
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