There are 44 diagonals in an 11 sided undecagon
There are: 0.5*(302-(3*30)) = 405 diagonals
1/2*15*(15-3) = 90 diagonals.
If you mean "How many diagonals can be drawn from one vertex of a figure with 16 sides", the formula is n-3, where "n" being the number of sides of the figure. So 16-3 = 13 diagonals that can be drawn from one vertex.
22-gon
It has: 0.5*(16squared-(3*16)) = 104 diagonals
252 diagonals
There are 119 diagonals.
It has 495 diagonals.
It has 54 diagonals
170
78
There are 44 diagonals in an 11 sided undecagon
0.5*(152-45) = 90 diagonals
A 20 sided polygon has 170 diagonals
There are 275 diagonals in a 25 sided polygon
39*36/2 = 702 diagonals.