Question

Prove that : sin^4(2x)=3/8-1/2cos4x+1/8cos8x Someone plzz help!!!

Answer 1

Sin^2 (2x) = (1 - cos(4x))/2
---> sin^4 (2x) = (1/4)(1 - cos4x)^2 = (1/4)(1 - 2cos4x + cos^2 (4x)) and replace cos^2(4x) by (1/2)(1+cos(8x)) --->answer