已知tana=-3/4,求2+sinacosa-cos^2a的值.

已知tana=-3/4,求2+sinacosa-cos^2a的值.
已知tana=-3/4,求2+sinacosa-cos^2a的值.

已知tana=-3/4,求2+sinacosa-cos^2a的值.
2+sinacosa-cos^2a
=2(sin^2a+cos^2a)+sinacosa-cos^2a
=2sin^2+sinacosa+cos^2a
=[2sin^2a+sinacosa+cos^2a]/(sin^2a+cos^2a)
=(2tan^2a+tana+1)/(tan^2a+1),(分子分母同除以cos^2a)
=(2*9/16-3/4+1)/(1+9/16)
=22/25