Question 15
Given a convex $n$-gon $P$ in the plane. For every three vertices of $P$, consider the triangle determined by them. Call such a triangle good if all its sides are of unit length.
Prove that there are not more than $\frac{2}{3} n$ good triangles.
Prove that there are not more than $\frac{2}{3} n$ good triangles.