Prove that :3sin−1x=sin−1(3x−4x3),xϵ[−12,12].
RHS : Let y=sin−1[3x−4x3]Put x=sinθ⇒θ=sin−1x...(i)∴y=sin−1[3sinθ−4sin3θ]=sin−1(sin3θ)As x ϵ[−12,12] ⇒−12≤x≤12 ⇒−12≤sinθ≤12⇒−π6≤θ≤π6 −π2≤3θ≤π2 −1≤sin3θ≤1∴y=3θ=3sin−1x=LHS By using (i)
Prove: 3sin−1x=sin−1(3x−4x3),x∈[−12,12]
Prove the following,
3sin−1x=sin−1(3x−4x3),xϵ[−12,12]