求下列三角函数值 1.sin11π/6 2.sin3π/5 3.sin(-5/3π) 4.cos(-11/9π) 5cos(-17_数学解答

求下列三角函数值 1.sin11π/6 2.sin3π/5 3.sin(-5/3π) 4.cos(-11/9π) 5cos(-17/4)π

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解答

1.sin11π/6=-1/2
2.sin3π/5 =sin72°
3.sin(-5/3π) =根号3/2
4.cos(-11/9π) =cos2/9π
5cos(-17/4)π=根号2/2