(sin75度-sin15度)*(cos15度+cos75du)的值

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(sin75度-sin15度)*(cos15度+cos75du)的值
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(sin75度-sin15度)*(cos15度+cos75du)的值
(sin75度-sin15度)*(cos15度+cos75du)的值

(sin75度-sin15度)*(cos15度+cos75du)的值
令x=75度,y=15度,=sinxcosy+sinxcosx-sinycosy-sinycosx
=sin(x-y)+cos(x+y)=sin60+cos90=根号3/2

(sin75-sin15)(cos15+cos75)
=(cos15-sin15)(cos15+sin15)
=cos^2(15)-sin^2(15)
=cos30
=√3/2

0 因为使用和差划积公式后该式等于四个三角函数值的积 其中一个是Cos90是零 得到结果为零