已知tana=3 sina^2-2sinacosa+3cosa^2
问题描述:
已知tana=3 sina^2-2sinacosa+3cosa^2
答
sin²a-2sinacosa+3cos²a=(sin²a-2sinacosa+3cos²a)/(sin²a+cos²a)
=(tan²a-2tana+3)/(tan²a+1)
=(9-6+3)/(9+1)
=6/10
=3/5