题目

证明tan^2x-sin^2x=tan^2 sin^2x

提问时间：2020-10-27

答案

tan^2x-sin^2x=sin^2x/cos^2x-sin^2x=
(1/cos^2x-1)sin^2x=[(1-cos^2x)/cos^2x]sin^2x=
[sin^2x/cos^2x]sin^2x=tan^2xsin^2x