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Question Number 47364 by olj55336@awsoo.com last updated on 09/Nov/18
anybodypleasehelpq...∫cos−1xdx
Commented by maxmathsup by imad last updated on 09/Nov/18
changementx=tgiveI=∫arccos(x)=∫2tarcos(t)dt=bypartst2arcost+∫t2dt1−t2but∫t21−t2dt=∫t.t1−t2dt=byparts−t1−t2−∫1−t2dtand∫1−t2dt=t=sinu∫cosucosudu=∫1+co(2u)2=u2+14sin(2u)=u2+12sinucosu=12arcsint+12t1−t2⇒∫arcos(x)=xarcos(x)−x1−x−12arcsin(x)−12x1−x+C=xarcos(x)−32x1−x−12arcsin(x)+C.
Answered by Smail last updated on 09/Nov/18
A=∫cos−1(x)dxbypartsu=cos−1(x)⇒u′=−12x×11−xv′=1⇒v=xA=xcos−1(x)+12∫x1−xdxB=∫x1−xdxt=x1−x⇒2tdt=1(1−x)2dxx=t2t2+1B=∫t×(2t(1−t2t2+1)2dt=2∫t2(t2+1)2dtt=tanu⇒dt=(1+tan2u)dudt(1+t2)2=du1+tan2uB=2∫tan2u×cos2udu=2∫sin2udu=∫(1−cos(2u))du=u−sin(2u)2+c=u−sin(u)cos(u)+cB=tan−1(t)−t1+t2+c=tan−1(x1−x)−x(1−x)+cA=xcos−1(x)+12tan−1(x1−x)−12x(1−x)+C
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