证明 sina^2+sinβ^2-sina^2sinβ^2+cosa^2cosβ^2=1

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证明 sina^2+sinβ^2-sina^2sinβ^2+cosa^2cosβ^2=1
证明 sina^2+sinβ^2-sina^2sinβ^2+cosa^2cosβ^2=1

证明 sina^2+sinβ^2-sina^2sinβ^2+cosa^2cosβ^2=1
sina^2+sinβ^2-sina^2sinβ^2+cosa^2cosβ^2
= sina^2+sinβ^2(1-sina^2)+cosa^2cosβ^2
= sina^2+sinβ^2cosa^2+cosa^2cosβ^2
= sina^2+cosa^2(sinβ^2+cosβ^2)
= sina^2+cosa^2
=1

sin²a+sin²β-sin²asin²β+cos²acos²β
=sin²a(1-sin²β)+sin²β+cos²acos²β
=sin²acos²β+cos²acos²β+sin²β
=cos²β(sin²a+cos²a)+sin²β
=cos²β+sin²β
=1

证明sin^2a+sin^2β+1>sina*cosa+sina+sinβ 证明 sina^2+sinβ^2-sina^2sinβ^2+cosa^2cosβ^2=1 证明sina sin(a+2b) - sinb sin(b+2a) =sin(a+b)sin(a-b) 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) 证明：(sina+cosa)^2=1+2sin^2acota 怎么证明2sinA*cosA=sin(2A) 证明：[sin(a-60)]^2+[sina]^2+[sin(a+60)]^2=3/2 证明三角函数等式sin(A+B)-sinA=2cos(A+B/2)sin(B/2) 证明sinA+sin(A+2π/3)+sin(A-2π/3)=0 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 sinA+sin(90°-A)+1/sinA-sin(90°-A)+1=cot(A/2) 请问这怎么证明, 证明：sin(2α+β)/sinα - 2cos(α+β)=sinβ/sinα sin(2a+β)/sina-2cos(a+β)=sinβ/sina 证明sin(2a+b)/sina-2cos(a+b)=sinb/sina 证明sin(2a+b)/sina-2cos(a+b)=sinb/sina 若3sin²a+sin²β=2sina,求2sina+sin²β 【证明】Sin A+sin B=2Sin 22