利用公式求下列三角函数値:(l).cos(-420°);(2).sin(-7/6π);(3).sin(-1300°);(4).cos(-79/6π)化简(1)sin(α+180°)cos(-α)sin(-α-180°)(2)sin^3(-α)cos(2π+α)tan(-α-π)要过程啊!
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利用公式求下列三角函数値:(l).cos(-420°);(2).sin(-7/6π);(3).sin(-1300°);(4).cos(-79/6π)化简(1)sin(α+180°)cos(-α)sin(-α-180°)(2)sin^3(-α)cos(2π+α)tan(-α-π)要过程啊!
利用公式求下列三角函数値:(l).cos(-420°);(2).sin(-7/6π);(3).sin(-1300°);(4).cos(-79/6π)
化简(1)sin(α+180°)cos(-α)sin(-α-180°)
(2)sin^3(-α)cos(2π+α)tan(-α-π)要过程啊!
利用公式求下列三角函数値:(l).cos(-420°);(2).sin(-7/6π);(3).sin(-1300°);(4).cos(-79/6π)化简(1)sin(α+180°)cos(-α)sin(-α-180°)(2)sin^3(-α)cos(2π+α)tan(-α-π)要过程啊!
(1).cos(-420°)=cos60°=1/2
(2).sin(-7/6π)=sin(π/6)=1/2
(3).sin(-1300°)=sin140°=sin40°
(4).cos(-79/6π)=-cos(π/6)=-√3/2
(1)sin(α+180°)=-sinα
cos(-α)=cosα
sin(-α-180°)=sinα
(2)sin^3(-α)=-sin^3(α)
cos(2π+α)=cosα
tan(-α-π)=-tanα
cos(-420)=cos(-360-60)=cos(-60)=cos(60)=1/2;
Sin(-7/6pai)=sin(-1/6pai)=-sin(1/6pai)=-1/2;
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