sin^2x - tan^2x = -sin^2x tan^2x
I kept working on tan on both sides, but cannot seem to get them to equal.
also this one
sin^4x + 2sin^2x.cos^2x + cos^4x = 1
I went :
sin^2x.sin^2x + 2sin^2x.cos^2x + cos^2x.cos^2x
I tried to make middle one sin2x didn't seem to get me anywhere.
Also tried changing one of the left sin^2x into 1-cos^2x and
one of the right cos^2x into 1-sin^2x
but they didn't cancel each other out.