tana=3,求1/sina^2+2sinacosa

问题描述:

tana=3,求1/sina^2+2sinacosa

1/sina^2+2sinacosa
=(sina^2+cosa^2)/(sina^2+2sinacosa)
=(tana^2+1)/(tana^2+2tana)
=10/16
=5/8