已知sin(x+5π)=3/5,则sinx
问题描述：
已知sin(x+5π)=3/5,则sinx
化简：cos(x-π/2)/sin(x+5π/2)·sin(x-2π)·cos(2π-x)=
已知sinα=2根号5/5,α∈(π/2,π)则tanα=
答
1,sin(x+5π)=-sinx=3/5,则sinx=-3/5
2,cos(x-π/2)/sin(x+5π/2)·sin(x-2π)·cos(2π-x)=sinx/cosx·sinx·cosx=sin²x
3,由α∈(π/2,π),sinα=2√5/5,cosα=-√5/5
tanα=-2
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