Question

Question #e17aa

Answer 1

`LHS=tan^2x-tan^2y`

`=sin^2x/cos^2x-sin^2y/cos^2y`

`=(sin^2xcos^2y-cos^2xsin^2y)/(cos^2xcos^2y)`

#=((sinxcosy+cosxsiny) (sinxcosy-cosxsiny)) /(cos^2xcos^2y)#

`=(sin(x+y)sin(x-y))/(cos^2xcos^2y)=RHS`

Proved