求证:tan^2α-sin^α=tan^2乘sin^2α
问题描述：
求证:tan^2α-sin^α=tan^2乘sin^2α
答
用a代替
左边=sin²a/cos²a-sin²a
=sin²a(1/cos²a-1)
=sin²a(1-cos²a)/cos²a
=sin²a*sin²a/cos²a
=sin²atan²a
=右边
命题得证