> 数学 >
sin21°cos81°+cos189°sin69°化简
人气：242 ℃　时间：2020-09-30 10:55:10
解答
sin21°cos81°+cos189°sin69°
=sin21°cos81°-cos9°sin69°
=sin21°sin9°-cos9°cos21°
=-cos(9+21)°
=-cos30°
=-√3/2
推荐
猜你喜欢
© 2024 79432.Com All Rights Reserved.
电脑版|手机版