I have the task of constructing a proof that shows how sinx/2 can be equal to plus or minus root((1-cosx)/2). Also how cosx/2 = plus or minus root((1+cosx)/2). I've been given the hint that it would involve the fact that sinx = plus or minus root((1-cos2x)/2) and cos2x = 1-2sin^2x. Any help I could get would be appreciated.
Edit: Here is a slight clarification if I typed poorly.