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已知sin(π/4+x)=12/13(π/4
人气:366 ℃ 时间:2020-06-17 03:56:20
解答
cos2x / cos(π/4-x)=cos2x/sin(π/2-π/4+x)
=(cos2x)/sin(π/4+x)
sin(π/4+x)=12/13
cos(π/4+x)=7/13(π/4sin(π/4+x)=12/13cos(π/4+x)=7/13(π/4
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