We have not understood the query that you have posted. We would request you to clarify / provide additional details so that we may answer this to the best of the ability.
Pl. check the question and send it again.If this is an identity, it must be true for all values of x.
If we put x=45 degrees, the LHS is not coming out to be equal to the RHS.
So do check and get back to us, we'll solve the question for you.