题干

△ABC的三个内角A,B,C的对边长分别为a,b,c,R是△ABC的外接圆半径,有下列四个条件:

①(a+b+c)(a+b﹣c)=3ab

②sinA=2cosBsinC

③b=acosC,c=acosB

2R(sin2Asin2C)=(2ab)sinB

有两个结论:甲:△ABC是等边三角形.乙:△ABC是等腰直角三角形.

请你选取给定的四个条件中的两个为条件,两个结论中的一个为结论,写出一个你认为正确的命题____

上一题 下一题 0.0难度 选择题 更新时间:2014-07-08 10:22:35

答案(点此获取答案解析)

(1)(2)→甲或(2)(4)→乙或(3)(4)→乙

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