Find dydxin the following questions:
y=sec−1(12x2−1),0<x<1√2
Let cos−1x=θ i.e.,x=cos θ
∴ y=sec−112x2−1⇒=sec−1(12cos2θ−1)⇒y=sec−1(1cos 2θ) ∵cos 2θ=2cos2θ−1
⇒ y=sec−1(sec 2θ) ⇒ =2θ ⇒ y=2cos−1x)
Differentiating both sides w.r.t. x, we get
⇒ dydx=2ddx(cos−1x)=−2√1−x2 (∵ ddx(cos−1x)=−1√1−x2)