求助，gwd 29-8

pimplekid · 发表于 2006-5-21 17:24:00

Q8:

S is a set of points in the plane. How many distinct triangles can be drawn that have three of the points in S as vertices?

(1) The number of distinct points in S is 5.

(2) No three of the points in S are collinear.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

题不太懂，做法就更不懂了，那位大侠给指点一下，感激不禁。 cllinear?什么意思？vertices?打错了？还是真有这个词？

hitlzc · 发表于 2006-5-21 19:40:00

金山词霸：

vertices
n.至高点, 头顶

此处为顶点之意思

collinear
adj.在同一直线上的, 同线的

hitlzc · 发表于 2006-5-21 19:44:00

选C.

因为不在同一直线上的任意三点可组成一个三角形。

所以组成三角形数量为C(5,3)

pimplekid · 发表于 2006-5-21 22:32:00

万分感谢！

bluetea · 发表于 2006-7-20 02:57:00

distinct triangles 是什么意思，如果是正五边形，所有的三角形都是一样的，如果不是正五边形，划分的三角形才不一样，是不是我想歪了，请教各位！^_^

mba06 · 发表于 2006-7-20 03:04:00

歪了歪了。位置不一樣也是distinct triangle﹐即便全等。

bluetea · 发表于 2006-7-20 04:22:00

OK，正过来了，不歪，谢了，呵呵

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