Question

sin^2x+sin^2tan^2x=tan^2x

Answer 1

I suspect there is a typo, it should probably read:
sin^2x+sin^2x tan^2x=tan^2x
Take the left-hand side:
sin²x+sin²x tan²x
=sin²x(1+tan²x)
=sin²x(sec²x)
=sin²x/cos²x
=tan²x