Answer to Question #123577 in Trigonometry for dangol

Question

prove that
(2cosθ−1)(2cosθ−1)(2cos2θ−1)=2cos4θ+1

Answer 1

As, we have to prove the given statement,thus it is true for all $\theta$ but clearly, for $\theta=0,π/2$ it's not true hence question is wrong.