若cos2a/sin((a-(π/4))=-(√2)/2,则cosa+sina的值为

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若cos2a/sin((a-(π/4))=-(√2)/2,则cosa+sina的值为若cos2a/sin((a-(π/4))=-(√2)/2,则cosa+sina的值为若cos2a/sin((a-(π

若cos2a/sin((a-(π/4))=-(√2)/2,则cosa+sina的值为
若cos2a/sin((a-(π/4))=-(√2)/2,则cosa+sina的值为

若cos2a/sin((a-(π/4))=-(√2)/2,则cosa+sina的值为
由cos2α/sin(α-π/4)=-(√2)/2,

cos2α=cos²α-sin²α
sin(α-π/4)=(√2)/2*(sinα-cosα)
则:
cos2α/sin(α-π/4)=cos²α-sin²α/((√2)/2*(sinα-cosα))=-(√2)/2
等式左边同时约去sinα-cosα,可得:
√2(sinα+cosα)=-(√2)/2
则有:sinα+cosα=-1/2