已知tana=2,求sin^2a-2sinacosa+2

问题描述:

已知tana=2,求sin^2a-2sinacosa+2

cos^2a=1/5
sin^2a-2sinacosa+2
=3sin^2a-2sinacosa+2cos^2a
=(3tan^2a-2tana+2)/cos^2a
=10/cos^2a
=50