please help me on the following:

Question

prove the identity.
cos4x = 1-8sin^x2cos^2x

Answer 1

I saw your question posted earlier, but could not determine the meaning of the right side

look at the " 8sin^x2 " part
That does not make any sense
check your typing.

For a solution look at the answer by Scarlet half way down this page
(Broken Link Removed)

The reply by Madhukar, which follows, ends up with the same result.
Perhaps you can take a hint from there after you have established what your right side has to be.