You can put this solution on YOUR website! (sin^2x-sin^2x*cos^2x)/cos^2x = tan^2x*sin^2x
(sin^2x-sin^2x*cos^2x)/cos^2x = (sin^2x/cos^2x)*sin^2x
Multiply by cos ^2
sin^2x-sin^2x*cos^2x = sin^2x*sin^2x
sin^2x*(1 - cos^2x) = sin^2x*sin^2x
sin^2*sin^2 = sin^2*sin^2
QED