how many diagnals does a 13-sided polygon (13-gon) have?

Answer 1

For an n-gon each vertex is connected as a diagonal to all but itself and the two adjacent vertices. So it is connected to n-3 vertices. This is true for all n vertices. Also note each diagonal has been counted twice, once from each end. So divide by 2.

Diagonals = n(n - 3)/2 = 13(10)/2 = 65

Answer 2

n(n-3)/2

n is 13 here

Ilusion