Question

$Cosx*Cos2x*Cos4x*Cos8x= frac{1}{16}$

Answer 1

16sinx*cosx*cos2x*cos4x*cos8x=sinx
8sin2xcos2x*cos4x*cos8x=sinx
sin16x=sinx
sin16x-sinx=0
2sin7,5xcos8,5x=0
sin7,5x=0
x=2Пk/15
cos8,5x=0
x=П/17(2k+1)