sina+sinb+siny=0.cosa+cosb-cosy=0,则cos(a-b)的值是,
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sina+sinb+siny=0.cosa+cosb-cosy=0,则cos(a-b)的值是,
![sina+sinb+siny=0.cosa+cosb-cosy=0,则cos(a-b)的值是,](/uploads/image/z/4752883-19-3.jpg?t=sina%2Bsinb%2Bsiny%3D0.cosa%2Bcosb-cosy%3D0%2C%E5%88%99cos%28a-b%29%E7%9A%84%E5%80%BC%E6%98%AF%2C)
-1/2,负2分之一
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再问: cosa+cosb+cosy=0 ����-1/2
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再问: cosa+cosb+cosy=0 ����-1/2
sina+sinb+siny=0.cosa+cosb-cosy=0,则cos(a-b)的值是,
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