已知cos(α-6/π)=12/13,π/6
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已知cos(α-6/π)=12/13,π/6
![已知cos(α-6/π)=12/13,π/6](/uploads/image/z/18328840-16-0.jpg?t=%E5%B7%B2%E7%9F%A5cos%EF%BC%88%CE%B1-6%2F%CF%80%EF%BC%89%3D12%2F13%2C%CF%80%2F6)
∵π/6<α<π/2
∴0<α-π/6<π/3
∴sin(α-π/6)=5/13
∴sinα=sin[(α-π/6)+π/6]
=sin(α-π/6)cosπ/6+cos(α-π/6)sinπ/6
=5/13*(√3/2)+12/13*(1/2)
=(5√3+12)/26
【过程已写出,】
∴0<α-π/6<π/3
∴sin(α-π/6)=5/13
∴sinα=sin[(α-π/6)+π/6]
=sin(α-π/6)cosπ/6+cos(α-π/6)sinπ/6
=5/13*(√3/2)+12/13*(1/2)
=(5√3+12)/26
【过程已写出,】
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