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=?](/uploads/image/z/19848220-52-0.jpg?t=%E8%AE%A1%E7%AE%97%EF%BC%9Asin%EF%BC%88a-30%C2%B0%EF%BC%89%C3%97sina%2Bcos%EF%BC%88a-30%C2%B0%EF%BC%89%C3%97cosa%3D%3F)
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
=(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
cos(a+30)cosa+sin(a+30)sina=?
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