才刚学··做不起都是化简哈··谢谢`最好有过程

1）sin^2a+sin^2b-sin^2a*sin^2b+cos^2a*cos^2b
=(sin^2a-sin^2a*sin^2b)+sin^2b+cos^2a*cos^2b
=(sin^2a*cos^2b+cos^2a*cos^2b)+sin^2b
=cos^2b+sin^2b
=1
2) tana*(cosa-sina)+sina*(sina+tana)/(1+cosa)
tana*(cosa-sina)=sina-sin^2a/cosa
sina*(sina+tana)/(1+cosa)=sin^2a*(1+1/cosa)/(1+cosa)=sin^2a/cosa
所以 原式=sina