If sin[cot−1(x+1)]=cos(tan−1x), then find x.Answer: x=−21SolutionExpress both sides as algebraic functions. If cot−1(x+1)=θ then cotθ=x+1 andsinθ=1+(x+1)21If tan−1x=ϕ then tanϕ=x and cosϕ=1+x21. Equate:1+(x+1)21=1+x21 ⇒ 1+(x+1)2=1+x2(x+1)2=x2 ⇒ 2x+1=0 ⇒ x=−21x=−21CBSE Class 12 Board · 2015 · Subjective