# trig

posted by
**Natash**
.

Prove that

cos4x=8cos^4x-8cos^2x+1

so I'm guessing you begin with the left side cos4x=cos2(2x) then im kinda lost

posted by
**Natash**
.

Prove that

cos4x=8cos^4x-8cos^2x+1

so I'm guessing you begin with the left side cos4x=cos2(2x) then im kinda lost