证明：[sin(a-60)]^2+[sina]^2+[sin(a+60)]^2=3/2

【证明】Sin A+sin B=2Sin 22 证明：[sin(a-60)]^2+[sina]^2+[sin(a+60)]^2=3/2 证明sin(a+b)sin(a-b)=sin^2 a-sin^2 b, 利用两角和差的余弦公式证明cosA-cosB=-2sin(A+B)/2 si(2)若三角形ABC三个内角A,B,C满足cos2A-cos2B=2sin^2C 判断三角形ABC形状第一题少的部分sin(A-B)/2 证明sina sin(a+2b) - sinb sin(b+2a) =sin(a+b)sin(a-b) 证明 sin^2A+sin^2B-sin^2A*sin^2B+cos^2A*cos^2证明 sin^2A+sin^2B-sin^2A*sin^2B+cos^2A*cos^2B=1 证明tan a/2=sin a/(1+cos a) 懂得进.证明,sina+sin(a+b)+sin(a+2b)+...sin(a+nb)=sin(a+ab/2)sin[(n+1)b/2]/sin(b/2) 三角形ABC 证明sin(A/2)*sin(B/2)*sin(C/2) 证明sin^2a+sin^2β+1>sina*cosa+sina+sinβ 证明 SIN²A+SIN²B-SIN²C=2SINASINBCOSC 怎样证明/sin a +sin b/ 证明Cos^A-Sin^A=1-2Sin^A=2Cos^A-1=cos^a-sin^a 数学求sin cos的题目把sin 2A改成 sin (A＋A)证明sin 2A－2 sin A cos A 证明sin^4a-cos^4a=sin^2a-cos^2a 证明：2sin(π+a)cos(π-a)=sin2a 证明：tan^2a-sin^2a=tan^2*sin^2a 证明sin^2atan^2a=tan^2a-sin^2a