α为锐角,且满足sinα=3cosα,则sinαcosα=
问题描述:
α为锐角,且满足sinα=3cosα,则sinαcosα=
答
sinα=3cosα
则
tana=3
则
sinαcosα
=sinαcosα/(sin²a+cos²a)
=tana/(tan²a+1)
=3/(9+1)
=3/10