作业帮(sin39° -sin21°)/(cos39°-cos21°)
来源：学生作业帮助网 编辑：作业帮 时间：2024/05/11 04:12:35
(sin39° -sin21°)/(cos39°-cos21°)
(sin39° -sin21°)/(cos39°-cos21°)
(sin39° -sin21°)/(cos39°-cos21°)
sin39° -sin21°
=sin(60°-21°)-sin21°
=√3/2*cos21°-1/2*sin21°-sin21°
=√3/2*cos21°-3/2 sin21°
=√3(1/2 *cos21°-√3/2 sin21°)
cos39°-cos21°
=cos(60°-21°)-cos21°
=1/2 cos21°+√3/2 sin21°-cos21°
=√3/2 sin21°-1/2 cos21°
所以原式= - √3
sin39°=cos21°，sin21°=cos39°，代入得-1
(sin39° -sin21°)/(cos39°-cos21°)
sin21°cos39°+cos21°sin39°=
(sin24°cos6°-sin66°sin6°)/(sin21°cos39°-cos21°sin39°)
求sin39°-sin21°/cos39°-cos21°的值急需过程,谢谢!
(sin24°cos6°-sin66°sin6°)/(sin21°cos39°-cos21°sin39°)化简后得
cos39°cos9°+sin39°sin9°=
sin21°cos24°+cos21°sin24°
sin21°cos81°-cos21°sin81°=?
求值sin21°cos24°+cos21°sin24°过程
sin21°cos81°-sin69°cos9°
求值sin21°cos24°+cos21°sin24°过程
求值：sin21°cos81°-sin69°cos9°
sin21°cos81°+cos189°sin69°化简
sin21°cos9°+cos21°sin9°=?
求sin21°+sin22°+...+sin289°的值.
求值：sin21/4π tan(-23/6π) cos1500°
sin39°-sin30°cos9°/cos39°-cos30°cos9°
设cos31°=α,则sin39°+tan149°=