作业帮求值：sin21°cos81°-sin69°cos9°
来源：学生作业帮助网 编辑：作业帮 时间：2024/11/27 19:16:57
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求值：sin21°cos81°-sin69°cos9°
求值：sin21°cos81°-sin69°cos9°
求值：sin21°cos81°-sin69°cos9°
sin21cos81-sin69cos9
=-sin21sin69cos81cos9
=[-sin21cos(90-69)][sin(90-81)cos9]
=(-sin21cos21)(sin9cos9)
=-(1/2sin42)(1/2sin18)
=-1/4sin42sin18
额,后面的忘了,自己算算吧,翻翻书,有这种类型的解法的.
sin21°cos81°-sin69°cos9°
=sin21°sin9°-cos21°cos9°
= - cos30°
=-√3/2
求值：sin21°cos81°-sin69°cos9°
sin21°cos81°-cos21°sin81°=?
sin21°cos81°-sin69°cos9°
sin21°cos81°+cos189°sin69°化简
sin21°cos81°+sin69°cos9°化简要详解
(sin24°cos6°-sin66°sin6°)/(sin21°cos39°-cos21°sin39°)
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sin6°sin42°sin66°sin78°求值
求值：sin6°sin42°sin66°sin78°
sin21度cos81度-sin69度cos9度=?
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cos54°cos9°+sin54°cos81°
三角运算cos54°cos351°+sin144°cos81°
(sin39° -sin21°)/(cos39°-cos21°)