Integrate the function.
∫sin−1(2x1+x2)dx.
Let I=∫sin−1(2x1+x2)dx
On putting x=tanθ, we get I=∫sin−1(2tanθ1+tan2θ)dx
=∫sin−1(sin2θ)dx(∵sin2θ=2tanθ1+tan2θ)=2∫θdx=2∫tan−1xdx[∵x=tanθ⇒θ=tan−1x]=2∫1II.tan−1Ixdx=2tan−1x∫1dx−2∫[ddxtan−1x∫1dx]dx
(using Integration by parts)
⇒I=2tan−1x.x−2∫[11+x2.x]dx
Put 1+x2=t⇒2x=dtdx⇒dx=dt2x
∴I=2xtan−1x−2∫[xt.dt2x]=2xtan−1x−∫1tdt=2xtan−1x−log|t|+C⇒I=2xtan−1x−log|1+x2|+C