若cosa-sina=-1/2,求sin2a
2个回答
sin2α=2sinαcosα
=1-(cosα-sinα)²
=1-(-1/2)²
=3/4.
相关问题
若sina+cosa=1/5,sin2a=?
(1-sina-cosa)(1-sina+cosa)/sin^2a_sina
若三角形ABC的内角满足sin2A=2/3 则sina+cosa=_____ (sinA+cosA)^2=1+sin2A
sina+cosa-1)(sina-cosa+1)/sin2a
若(sina+cosa)/(sina-cosa)=2,则sin(a-5派)*sin(3派/2-a)等于?
证明(1+sin2a)/(cosa+sina)=cosa+sina
若sina - cosa=1/5 ,则sin2a=______?
证明sin2a/(1+sina+cosa)=sina+cosa-1
sina+cosa=1/3,求sin2a
(sina+cosa-1)(sina-cosa+1)/sin2a = tana/2 证明