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=

sinα=3cosα

tana=3

sinαcosα
=sinαcosα/(sin²a+cos²a)
=tana/(tan²a+1)
=3/(9+1)
=3/10