A polygon has 1325 diagonals. How many vertices does it have?
(In reply to
Common sense by Jane Doe)
An octagon has 20 diagonals: Each of the 8 vertices can connect to any of 5 of the other vertices (just not to itself nor to either immediate neighbor). So far we've counted 40; but we've counted each one twiceonce in each direction, so there are 20. A diagonal of a polygon should not be confused with the diameter of a circle. The latter must go through the center, but the former need not.

Posted by Charlie
on 20040131 13:50:59 