已知sinx=-根号5/5,x属于(派,3/2派),则sin(2x-派/4)=
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![已知sinx=-根号5/5,x属于(派,3/2派),则sin(2x-派/4)=](/uploads/image/z/12614275-19-5.jpg?t=%E5%B7%B2%E7%9F%A5sinx%3D-%E6%A0%B9%E5%8F%B75%2F5%2Cx%E5%B1%9E%E4%BA%8E%28%E6%B4%BE%2C3%2F2%E6%B4%BE%29%2C%E5%88%99sin%EF%BC%882x-%E6%B4%BE%2F4%EF%BC%89%3D)
已知sinx=-根号5/5,x属于(派,3/2派),则sin(2x-派/4)=
已知sinx=-根号5/5,x属于(派,3/2派),则sin(2x-派/4)=
已知sinx=-根号5/5,x属于(派,3/2派),则sin(2x-派/4)=
sin(2x-π/4)=sin2xcosπ/4-cos2xsinπ/4=根号2/2(sin2x-cos2x)=根号2/2(2sinxcosx-(cosx)^2+(sinx)^2)
因为x属于(派,3/2派) 所以cosx=-2根号5/5,代入上式就可以了