请教各位大神一道数学题

RamosZou

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.

答案是C，但是没看懂为什么啊！  请教各位大神啦   感谢!   

Kitwong

（1）不同的点的数量为5
（2）没有3个点是同一直线上的

构成三角形的三个点肯定不是同一直线的~ So 可以确认三角形数量

windowshade

(1) 5 in a row=>0 vs 4 in a row=>more than 1 ->insufficient
(2) C(n)(3), no n, -> insufficient
(1)+(2) C(5)(3) good