求值.若sina=2cosa,则1/(sin^2a+sinacosa)=
sina+cosa/sina-cosa=2 求sin^2a-2sinacosa+1
若sina+cosa=1/2则sinacosa=?sina+cosa=1/2 两边平方sin^2a+cos^2a+2si
已知3sina=-cosa,求值 (1)sina-3cosa/sina+3cosa (2)1+sinacosa
已知sina+cosa=1/2,求sinacosa和sin^3a+cos^3a
若sina+cosa=1/2则sinacosa=?若sinacosa=1/4且a是第三象限角,则sina+cosa=?
tana=2,求2sina+cosa/sina-cosa和sin^2a-2Sinacosa+3cos^2a
tana=2 5-2sinacosa=?(sina+cos^3a)/cosa+sin^3a=?
已知sina+cosa=0,求sin^2a+2sinacosa+cos^2a
已知sina+cosa=根号2,求sinacosa,tana,sin^4a+cos^4a
证明1+sina+cosa+2sinacosa/1+sina+cosa=sina+cosa,
若tana=2,求(2sina+cosa)/(sina-cosa)和sin平方a-2sinacosa+3cos平方a的值
已知2sina=-cosa,则1+2sinacosa/(sina-cosa)=?