求下列三角函数值(求过程)
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发布时间：2024-10-24 00:21
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热心网友
时间：2024-11-10 23:08
1.sin(-16Π/3)=sin(-6Π 2/3×Π)=sin(2/3×Π)=√3/2 2.cos(-945°）=cos(-1080° 135°)=cos(135°)=-√2/2 3.cos(π α）=-cosα=-1/2 cosα=1/2sina=√1-(1/2)=±√3/2 sin(-α)=±√3/2 4.1/2sin2x √3/2cos2x-√3/2 =sin(2x Π/6)-√3/2 (1).f(25π/6)=sin(50Π/6 Π/6)-√3/2=sin(48Π/6 3Π/6)-√3/2=1-√3/2 (2).f(α/2)=1/4-√3/2 f(α/2)=sin(α Π/6)-√3/2=1/4-√3/2 说明sin(α Π/6)=1/4 sinαcosΠ/6 cosαsinΠ/6=√3/2sinα 1/2cosα=1/4 √3sinα cosα=1/2 sinα cosα=1 联立上面两式得 sinα=(√3±√15)/8 因为α属于（0，π),则sinα>0,所以sinα=(√3 √15)/8
