Prove that

Answer:

= cosx cos2x cos4x cos8x
Multiply and divide by 2sinx, we get

We know that,
sin 2x = 2 sinx cosx
Replacing x by 2x, we get
sin 2(2x) = 2 sin(2x) cos(2x)
or sin 4x = 2 sin 2x cos 2x