It is an octagon
A polygon with n sides has n*(n-3)/2 diagonals (not diagnols!).So, an octagon has 8*5/2 = 20 of them.
44
None
A square, a rhombus and a kite
It has: 0.5*(100^2-(3*100)) = 4850 diagonals
The rule is: 0.5*(N2-3N) = number of diagonals
a triangle has 0 diagnols
A polygon with 20 sides is an icosagon.
A 20 sided polygon is an 'icosagon'
There is no such shape. And unfortunately the word is too much like two terms to determine which of them you mean.If the polygon has n sides (n>3), then it has n*(n-3)/2 diagonals.
A 20-sided polygon is an icosagon.(see related link)
Duodecagon <--wrong... a duodecagon is a 12-sided polygon. icosagon is a 20 sided polygon.