1.化简sin25/12πsin11/6π－cos25/12πcos11/6π的值是2.已知sina=15/17,a是第二象限角,则cos[a－π/3]= cos[a+π/3]=

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1.化简sin25/12πsin11/6π－cos25/12πcos11/6π的值是2.已知sina=15/17,a是第二象限角,则cos[a－π/3]= cos[a+π/3]=

1.化简sin25/12πsin11/6π－cos25/12πcos11/6π的值是2.已知sina=15/17,a是第二象限角,则cos[a－π/3]= cos[a+π/3]=
1.化简sin25/12πsin11/6π－cos25/12πcos11/6π的值是
2.已知sina=15/17,a是第二象限角,则cos[a－π/3]= cos[a+π/3]=

1.化简sin25/12πsin11/6π－cos25/12πcos11/6π的值是2.已知sina=15/17,a是第二象限角,则cos[a－π/3]= cos[a+π/3]=
sin(a+b)=sin(a)*cos(b)+cos(a)*sin(b)
sin(a-b)=sin(a)*cos(b)-cos(a)*sin(b)
cos(a+b)=cos(a)*cos(b)-sin(a)*sin(b)
cos(a-b)=cos(a)*cos(b)+sin(a)*sin(b)
那么
1,sin25/12πsin11/6π-cos25/12πcos11/6π
= - cos(25/12π+11/6π)
= - cos(47/12π)
2,sina=15/17 得到 cosa=√(1-(15/17)^2)=8/17
cos(a-π/3)
= cos(a)cos(π/3) + sind(a)sin(π/3)
=8/17 * 1/2 + 15/17 * √3/2
=4/17+15√3/34

1.化简sin25/12πsin11/6π－cos25/12πcos11/6π的值是2.已知sina=15/17,a是第二象限角,则cos[a－π/3]= cos[a+π/3]= sin11/π*sin11/3π*sin11/5π分之sin11/10π*sin11/8π*sin11/6π 等于多少其中*是乘号 /是几分之几~ sin25π/6等于? 1.cos80ºcos35º+cos10ºcos55º=_____2.sin25/12πcos11/6π-cos25/12πsin11/6π=____3.已知sin=2/3,a∈(π/2,π),则cos(π/3+a)=____4.sin(α-β)cosβ+cos(α-β)sinβ=_____5.已知向量→ 绕原点旋转45º到→的位置,则P' Sin11π/6 sin 5π/6 sin11π/2 像这样的三角函数怎么求值 一道很基础的三角函数化简题sin25π/6+cos25π/3+tan25π/4 化简： 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 求值:sin(-31π/6)-cos(-10π/3)-sin11π/4 sin25π/6+cos25π/3+tan(-25π/4) 计算sin25/6π+tan9/4π-cos19/3π 计算sin25/6π+tan9/4π-cos19/3π sin25/6π+cos4/3π等于多少? sin25π/3 结果是多少. 计算：sin25π/6+cos25π/4+tan(-25π/4)+sin(-26π/3) sin25π/6 + cos25π/3 + tan(-25π/4)这题怎么算? 求sin25π/6+cos25π/3+tan（-25π/4）的值? 计算,sin25π/6+cos25π/3+tan(-25π/4) sin25π/6+cos25π/3+tan25π/4等于多少?