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.