1) If y=sec(tan−1x) then dydx at x=1 is equal to A) 1√2 B) 12 C) 1 D) √2 Answer: Option AExplanation:Given , y= sec {tan-1 x) Let tan−1x=θ⇒x=tanθ ∴ y=secθ=√1+x2 On differentiating w.r.t x, we get dydx=12√1+x22x At x=1, dydx=1√2