已知cos²α-cos²β=1/3,求sin(α+β)·sin(α+β)
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已知cos²α-cos²β=1/3,求sin(α+β)·sin(α+β)
已知cos²α-cos²β=1/3,求sin(α+β)·sin(α+β)
已知cos²α-cos²β=1/3,求sin(α+β)·sin(α+β)
cos²α-cos²β
=(cos2α+1)/2-(cos2β+1)/2
=(cos2α-cos2β)/2
=-sin(α+β)sin(α-β) =1/3
则,sin(α+β)sin(α-β) = -1/3
题目打错了,应该求sin(α+β)sin(α-β)