Mathematics - Trigonometric Equation Question with Solution | TestHub

${\prod }_{j=m}^n\cos (2^j\theta )=\frac{\sin (2^{n+1}\theta )}{2^{n-m+1}\sin (2^m\theta )}$ whenever the denominator is nonzero. Evaluate ${\prod }_{j=3}^{10}\cos (2^j\pi /10)$.