1. The problem statement, all variables and given/known data prove that cos^4(x)= 3/8 +1/2(cos2x)+1/8(cos4x) 2. Relevant equations 3. The attempt at a solution i attempted to change the cos2x to 2cos^2(x)-1.....then made all them over 8....and now im stuck......another question....if i multiply 2cos(4x) by 2, do i multiply the 2 and the 4x? or just he 4x?