Geometry

# How many diagonals are in a Decagon?

###### Wiki User

###### 2015-11-01 19:57:26

35.

## Related Questions

###### Asked in Math and Arithmetic, Geometry

### How many diagonals are there in a decagon?

A decagon has 35 diagonals. A Nonagon has 27 diagonals. An
Octagon has 20 diagonals. A Heptagon has 14 diagonals. A Hexagon
has 9 diagonals. A Pentagon has 5 Diagonals. A Square has 2
Diagonals. A triangle has 0 Diagonals.
Do you get the point?
0+2+3+4+7+8. Starting with the triangle.
you don't need to start with the triangle because it is 0
diagonals and will not count when you add it up anyways. And don't
call it a square, call it a quadrilateral.
Shut up
------
-Imagine a hexagone
-There are two vertices at the top which make a horizontal
line
- Opposite them there are 2 vertices on the bottom which we can
draw straight lines to
therefore
-There would have been 6 connections per point, but we
eliminated 3
(n-3)
--
-The connections occur for every vertex in the shape
therefore
n(n-3)
--
We don't want to draw the same connections twice once we get
around to vertices on the opposite side of the shape
therefore
n/2(n-3)
where n is the number of faces
This may be applied to many if not all polygons. A Decagon has
36 sides not 35...
There are 35 diagonals in a 10 sided decagon