You can
put this solution on YOUR website! How many diagonal lines are there in a 130-sided
polygon?
The set of all pairs of vertices includes all the
diagonals plus all of the 130 sides. So to find
the number of diagonals, we calculate the number
of combinations of 130 vertices taken 2 at a time
and then subtract the 130 sides. So the answer is
C(130,2) - 130 =
130·129/2·1 - 130 =
8385 - 130 =
8255 diagonal lines
Edwin
