tanα=-2,则sin平方α+sinαcosα=?
问题描述：
tanα=-2,则sin平方α+sinαcosα=?
答
(sina)²+sinacosa
=sin²a+sinacosa
=(sin²a+sinacosa)/(sin²a+cos²a)
=(tan²a+tana)/(tan²a+1)
=(2²+2)/(2²+1)
=6/5
=5分之6