Find dydxin the following questions:
y=cos−1(1−x21+x2),0<x<1.
Let tan−1x=θi.e.,x=tant θ
∴ y=cos−1(1−x21+x2)=y=cos−1(1−tan2θ1+tan2θ) (∵ 1−tan2θ1+tan2θ=cos 2θ)
⇒ y=cos−1(cos 2θ)=2 tan−1x
Differentiating both sides w.r.t. x, we get
dydx=2ddx(tan−1x)=21+x2 (ddxtan−1x=11+x2)