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

证明：[sin(a-60)]^2+[sina]^2+[sin(a+60)]^2=3/2 证明sinA+sin(A+2π/3)+sin(A-2π/3)=0 sina(cosa)^3=1/4sin 2a+1/8sin 4a证明过程 证明三角函数等式sin(A+B)-sinA=2cos(A+B/2)sin(B/2) 证明sin(2a+b)/sina-2cos(a+b)=sinb/sina 证明(sinA)^2+[sin(A+2π/3)]^2+[sin(A-2π/3)]^2=3/2 【证明】Sin A+sin B=2Sin 22 sinb/sina=cos(a+b),证明3sinb=sin(2a+b) 已知3SIN^2A+2SIN^2B=5SINA,求SIN^2A+SIN^2B范围 1- sin(2π/3 - a)/sina sinA+sin(120-A)=3/2 求A度数 证明sin(a+b)sin(a-b)=sin^2 a-sin^2 b,