1

Part of 2010 IMAC Arhimede

Problems(1)

n distinct triangles from 3n points

Source: IMAC Arhimede 2010 p1

3n

points are given (

n\ge 1

) in the plane, each

3

of them are not collinear. Prove that there are

n

distinct triangles with the vertices those points.

combinatoricscombinatorial geometrypointscollinear