Question

how to solve this identity (cosx)^4 -(Sin X)^4 = Cos(2x)

Answer 1

factor

Answer 2

\[(a^4-b^4)=(a^2+b^2)(a^2-b^2)\]

Answer 3

Ok, I just factor that and simplify?

Answer 4

yeah
i used \(a\) for cosine and \(b\) for sine

Answer 5

the first term \[a^2+b^2\] is the same as \[\cos^2(x)+\sin^2(x)\] which is 1

Answer 6

so you really just get \[\cos^2(x)-\sin^2(x)\]

Answer 7

I'm trying to see what you are telling me to do? a little confuse.