证明tan^2-sin^2=tan^2sin^2

题目

证明tan^2-sin^2=tan^2sin^2
急用!

答案

tan^2-sin^2-tan^2sin^2
=tan^2(1-sin^2) -sin^2
=tan^2cos^2-sin^2
=sin^2-sin^2
=0
所以tan^2-sin^2=tan^2sin^2