A diagonal of a polygon is an segment between two non-adjacent vertices of the polygon. How many diagonals does a regular 45-sided polygon have? Pick
A) 875  B) 945  C) 1425  D) 2025  E) 2500

Rationale: "there ' s a direct formula for this . number of diagonals in a regular polygon = [ n * ( n - 3 ) ] / 2 , n = number of sides of the regular polygon . here , n = 45 . plugging it in , we get 945 diagonals ! answer ( b ) ."
Answer: B