已知tana=2,求sin^2a-2sinacosa+2
问题描述:
已知tana=2,求sin^2a-2sinacosa+2
答
cos^2a=1/5
sin^2a-2sinacosa+2
=3sin^2a-2sinacosa+2cos^2a
=(3tan^2a-2tana+2)/cos^2a
=10/cos^2a
=50