诱导公式.1.已知cos31°=a,则sin239°tan149°=_____2.求三角函数值 (1)cos(-17π/4) (2)sin26π/3 (3)cos1650° (4)sin1740°3.[sin(180°-405°)sin(270°-765°)]/[sin(90°+45°)tan(270°+45°)]=______4.当角

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诱导公式.1.已知cos31°=a,则sin239°tan149°=_____2.求三角函数值 (1)cos(-17π/4) (2)sin26π/3 (3)cos1650° (4)sin1740°3.[sin(180°-405°)sin(270°-765°)]/[sin(90°+45°)tan(270°+45°)]=______4.当角
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诱导公式.1.已知cos31°=a,则sin239°tan149°=_____2.求三角函数值 (1)cos(-17π/4) (2)sin26π/3 (3)cos1650° (4)sin1740°3.[sin(180°-405°)sin(270°-765°)]/[sin(90°+45°)tan(270°+45°)]=______4.当角
诱导公式.
1.已知cos31°=a,则sin239°tan149°=_____
2.求三角函数值 (1)cos(-17π/4) (2)sin26π/3 (3)cos1650° (4)sin1740°
3.[sin(180°-405°)sin(270°-765°)]/[sin(90°+45°)tan(270°+45°)]=______
4.当角α,β满足的条件为_____,有sinα=sinβ

诱导公式.1.已知cos31°=a,则sin239°tan149°=_____2.求三角函数值 (1)cos(-17π/4) (2)sin26π/3 (3)cos1650° (4)sin1740°3.[sin(180°-405°)sin(270°-765°)]/[sin(90°+45°)tan(270°+45°)]=______4.当角
1) -(1-a^2) ½ -a/(1-a^2)½
2) 2½ /2 3½/2 -1/3½ 3½/2
3)-2½/2
4)α+β=?π(?=奇数)

先把那些角都化简
sin(-α) = -sinα
cos(-α) = cosα
tan (—a)=-tanα
sin(π/2-α) = cosα
cos(π/2-α) = sinα
sin(π/2+α) = cosα
cos(π/2+α) = -sinα
sin(π-α) = sinα
...

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先把那些角都化简
sin(-α) = -sinα
cos(-α) = cosα
tan (—a)=-tanα
sin(π/2-α) = cosα
cos(π/2-α) = sinα
sin(π/2+α) = cosα
cos(π/2+α) = -sinα
sin(π-α) = sinα
cos(π-α) = -cosα
sin(π+α) = -sinα
cos(π+α) = -cosα
tanA= sinA/cosA
tan(π/2+α)=-cotα
tan(π/2-α)=cotα
tan(π-α)=-tanα
tan(π+α)=tanα
诱导公式记背诀窍:奇变偶不变,符号看象限

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