There are 2
27 diagonals
Yes every parallelogram has bisecting diagonals
27
It is: 0.5*(92-3*9) = 27 diagonals in a 9 sided nonagon
Not in general.
A Nonagon has 36 diagonals
24 diagonals
It has 27 diagonals
There are 2
9 diagonals
27 diagonals
27
Yes every parallelogram has bisecting diagonals
27
It is: 0.5*(92-3*9) = 27 diagonals in a 9 sided nonagon
None, if it is an irregular octagon.