证明1+sina=2cos^2(45-a/2)
证明(1-cos^2a)/(sina+cosa)-(sina+cosa)/(tan^2a-1)=sina+cosa
证明(1-cos^2a)/(sina-cosa)-(sina+cosa)/(tan^2-1)=sina+cosa
证明 cosa/(1+sina0-sina/(1+cosa)=2(cosa-sina)/(1+sina+cos)
证明1-COS^2α/(SINα-COSα)-SINα+COSα/(TAN^2a-1)=SINa+COSa
证明sin(2a+b)/sina-2cos(a+b)=sinb/sina
证明:(sin a/2+cos a/2)平方=1+sina
在三角形ABC中,证明2sinA*sinB=-[cos(A+B)-cos(A-B)]
(sinA+sinB)/(cos A +cos B) =tan (A+B)/2 怎么证明?
证明sina*sinb=[cos(a-b)-cos(a+b)]/2
三角函数线证明tan(a/2)=sina/( 1+cosα)
已知sin a+cos a=1/2 sina*cosa=?cos a/sina+sina/cosa=?
如何证明sinA+sinB=2sin((A+B)/2)cos((A-B)/2)