2AB*AC(AB,AC为向量)=根号3*AB*AC AB,AC为向量的模)
====>cosA=√3/2===>A=30º
根号3*AB*AC AB,AC为向量的模)=3BC^2
====>cb=√3a²===>sinCsinB=√3sin²A=√3/4
又sinCsinA=[cos(B-C)]/2-[cos(B+C)]/2=[cos(B-C)]/2+[cosA]/2
=[cos(B-C)]/2+√3/4=√3/4
∴[cos(B-C)]/2=0===>B-C=90º或C-B=90º
又B+C=180-30=150º
∴B=120º,C=30º或B=30º,C=120º
在△ABC中,已知2AB*AC(AB,AC为向量)=根号3*AB*AC AB,AC为向量的模)=3BC^2,求角A,B,C的大小
在△ABC中,已知2AB*AC(AB,AC为向量)=根号3*AB*AC AB,AC为向量的模)=3BC^2,求角A,B,C的大小
数学人气:439 ℃时间:2019-11-24 11:57:26
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