Idid this problem and i was told i did it wrong how do i fix it? ?

  (1/8)(cos(4x) -4cos(2x) +3)

Step-by-step explanation:

Your answer is correct as far as it goes. You now need to use a power-reducing identity on the cos(2x)² term in your answer. The appropriate one is ...

  cos(x)² = (1/2)(1 +cos(2x))

In the context of this problem, using this formula gives you ...

  sin(x)⁴ = (1/4)(1 -2cos(2x) +(1/2)(1 +cos(4x))

  sin(x)⁴ = (1/8)(cos(4x) -4cos(2x) +3)

the two may have that, even a breakdown is probably offered