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来源：学生作业帮助网 编辑：六六作业网 时间：2024/12/23 19:07:09
已知0已知0已知0sin(π/4+α+3π/4+β)=sin(π/4+α)cos(3π/4+β)+cos(π/4+α)sin(3π/4+β)=-84/85=sin(π+α+β)=-sin(α+β)所以
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已知0<β<π/4 ,π/4<α<3π/4,cos(π/4+α)=-3/5 sin(3π/4+β)=8/17 求sin(α+β）
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sin(π/4+α+3π/4+β)=sin(π/4+α)cos(3π/4+β)+cos(π/4+α)sin(3π/4+β)=-84/85=sin(π+α+β)=-sin(α+β)
所以sin(α+β)=84/85