计算:sin(a-30°)×sina+cos(a-30°)×cosa=?

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计算:sin(a-30°)×sina+cos(a-30°)×cosa=?
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计算:sin(a-30°)×sina+cos(a-30°)×cosa=?
计算:sin(a-30°)×sina+cos(a-30°)×cosa=?

计算:sin(a-30°)×sina+cos(a-30°)×cosa=?
sin(a-30°)×sina+cos(a-30°)×cosa
=(sinacos30°-cosasin30°)*sina+(cosasin30°+sinacos30°)*sina
=(√3/2sina-1/2cosa)*sina+(1/2cosa+√3/2sina)*sina
=√3/2sin²a-1/2sinacosa+1/2sinacosa+√3/2sin²a
=√3sin²a