Find the number of diagonals of a seven-sided convex polygon.

Find the number of diagonals of a : pentagon .

Find the number of diagonals of a : octagon .

The number of diagonals in a convex polygon with number of sides 4 are:

The number of diagonals of a polygon of 20 sides is :

The number of diagonals of a regular polygon of n sides are:

In a polygon, no three diagonals are concurrent. If the total number of points of intersection of diagonals interior to the polygon is 70, then the number of diagonals of the polygon is

In a polygon the number of diagonals is 54. The number of sides of the polygon, is A. 10 B. 12 C. 9 D. None of these

In a polygon the number of diagonals 77. Find the number of sides of the polygon.