1sorry there is some mistake in question i edited it
look it now
3 Answers
11??????????
what?? is this a question???
wat do mean by0 no of permutation in a polygon?
111ok
the polygon has n sides
so for making a diagonal we have to have two points
therefore no of such cases is selecting 2 points out of n points i polygon
=nC2
but out of these some cases are there in which we have selected two adjacent points .....no of such adjacent points =n
therefore total no of diagonals= nC2 - n
ans= n(n-3)2