Shades...I think this is supposed to be.....
[sec^2x - 1 ] / sec^2 x = sin^2x
It's usually best to break these tihngs down in terms of sine and/or cosine .....or use an identity to get something in the form of the tangent which can be expressed in terms of sine and cosine......so we have
tan^2x / sec^2x = [remember that sec^2x - 1 = tan^2x]
[sin^2x / cos^2x] / [1 / cos^2x] =
[sin^2 x / cos^2x ] * [ cos^2 x / 1] = [the cos^2x cancels on top/bottom]
sin^2x and this = the right side
