证明tan^2-sin^2=tan^2sin^2急用!

tan^2 - sin^2
= sin^2/cos^2 - sin^2
= (sin^2 - sin^2*cos^2) / (cos^2)
= sin^2(1 - cos^2) / (cos^2)
= sin^2(sin^2) / (cos^2)
= tan^2*sin^2

tan^2-sin^2=（sin^2-sin^2cos^2)/cos^2=sin^2(1-cos^2)/cos^2=sin^2*sin^2/cos^2=tan^2sin^2

证明：∵左边=tan^2-sin^2
= sin^2/cos2-sin^2
=sin^2（1/cos^2-1）
=sin^2（1/cos^2-cos^2/cos^2）
=sin^2（1-cos^2/cos^2）
=sin^2（sin^2/cos^2）
=sin^2tan^2
=右边
∴原式成立！

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

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