sin21°cos189°-sin69°sin9°的值为
来源:学生作业帮 编辑:神马作文网作业帮 分类:数学作业 时间:2024/09/25 14:30:18
sin21°cos189°-sin69°sin9°的值为
用到的公式:[cos(180°+A)=-cosA/sin(90°-A)=cosA/sin(A+B)=sinAcosB+cosAsinB]
因为cos189°=cos(180°+9°)=-cos9°
和sin69°=sin(90°-21°)=cos21°
所以
sin21°cos189°-sin69°sin9°
=-sin21°cos9°-cos21°sin9°
=-(sin21°cos9°+cos21°sin9°)
=-sin(21°+9°)
=-sin30°
=-(1/2)
++++希望可以帮助你 我也可以加分哟 哈哈
因为cos189°=cos(180°+9°)=-cos9°
和sin69°=sin(90°-21°)=cos21°
所以
sin21°cos189°-sin69°sin9°
=-sin21°cos9°-cos21°sin9°
=-(sin21°cos9°+cos21°sin9°)
=-sin(21°+9°)
=-sin30°
=-(1/2)
++++希望可以帮助你 我也可以加分哟 哈哈
求值(sin9°cos15°-sin24°)/(sin9°sin15°+cos24°)
cos15°sin9°+sin6°/sin15°sin9°—cos6°=
化简COS8°-SIN17°SIN9°/COS9°
(Sin15Cos9°—Cos66°)/(Sin15°Sin9°+Sin66°)可以化简为?要过程
计算:sin21°+sin22°+sin23°+…+sin287°+sin288°+sin289°.
化简(sin15°cos9°-cos66°)/(sin15°sin9°+sin66°)的结果是?
求值:(sin9°+sin6°cos15°)/(cos9°-sin6°sin15°)
计算:sin21°+sin22°+sin23°+…+sin288°+sin289°+sin290°= ___ .
1.比大小:tan21°和tan31°;2.sin21°和cos21°;3.cos21°和cos22°
急求下列三角函数值sin9°52′22″sin10°30′25″sin10°32′22″
不求值,分别比较下列各组中两个三角函数值的大小(1)sin21/5π与sin42/5π sin1/5与cos5
已知cos(α-π/6)+sinα=4/5∫3,求sin9α+7π/6)的值.