已知sin(x+π/4)=-1/3 则cos(x-π/4)的值为详细的步骤 谢谢

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已知sin(x+π/4)=-1/3 则cos(x-π/4)的值为详细的步骤 谢谢
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已知sin(x+π/4)=-1/3 则cos(x-π/4)的值为详细的步骤 谢谢
已知sin(x+π/4)=-1/3 则cos(x-π/4)的值为
详细的步骤 谢谢

已知sin(x+π/4)=-1/3 则cos(x-π/4)的值为详细的步骤 谢谢
解由sin(x+π/4)=-1/3
得cos[π/2-(x+π/4)]=-1/3
即cos(π/4-x)=-1/3
即cos[-(x-π/4)]=-1/3

cos(x-π/4)=-1/3

依正弦余弦函数图像得:sin x =cos(x-π/2)
所以sin(x+π/4)=-1/3=cos(x-π/4)