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Suppose there are $n$ points equally spaced ( i.e. the distances between two consecutive points are same) on the circumference of a circle. Now if we join each point with every other points by a straight line then how many points of intersection will be there ?

I tried to find a recurrance relation. Is there a recurrance relation to solve for the number of points of intersection ?

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From OEIS: Number of intersections of diagonals in the interior of regular n-gon.

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Since there are n vertices and picking any 2 diagonals create one intersection with each other , along with using the fact 4 vertices determine a given two diagonals, we can safely say there are nC4 combinations of interior intersections on the interior of an n-gon