Question

2sin(180+x)sin(90+x)/cos⁴x-sin⁴x

Answer 1

2sin(180+x)sin(90+x)/(cos^4x - sin^4x)

2(-sinx)(cosx) / (cos^2x - sin^2x)(cos^2x + sin^2x
-sin2x/cos2x
-tan2x