1951 AMC 12 第 27 题

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所有题目均经美国数学协会(MAA)官方合法授权使用。

27.

过三角形内一点,从三个顶点分别向对边画直线,将原三角形分成六个三角形区域。则:

Through a point inside a triangle, three lines are drawn from the vertices to the opposite sides, forming six triangular sections. Then:

每一对相对的三角形都相似

The triangles are similar in opposite pairs

每一对相对的三角形都全等

The triangles are congruent in opposite pairs

每一对相对的三角形面积都相等

The triangles are equal in area in opposite pairs

形成三个相似的四边形

Three similar quadrilaterals are formed

以上关系均不成立

None of the above relations is true

答案:E
知识点:三角形面积反例
难度评级:1470
小提示:

内点及三条顶点与对边相交的直线都是任意的

The interior point and the three cevians are arbitrary

大提示:

将该点移到非常靠近某一边的位置,检验所声称的相对区域面积关系

Move the point very close to one side to test the claimed opposite-area relation

解答:

题目没有给出任何角度或长度条件,足以保证相对区域相似或全等。它们的面积也不必相等:将内点放在非常靠近某一边的位置,可使邻接该边的区域任意小,却不会迫使其相对区域也变小。六个区域中也没有四边形。

因此,正确答案是 E

No angle or length condition forces opposite sections to be similar or congruent. Their areas also need not match: placing the interior point very close to one side makes the sections adjoining that side arbitrarily small without forcing their opposite sections to be small. No quadrilaterals are among the six sections.

Thus, the correct answer is E.

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