The formula for the number of diagonals (that is, lines joining non-adjacent vertices) belonging to any shape is n(n-3)/2. Therefore, an eighteen-sided polygon has 18 x (18 - 3)/2 = 135 diagonals.
All I can tell you is that a 16 sided shape is called a Hexadecagon
Tetrahaidecahedron
Octadecadron
If it is a 2 dimentional shape it is called an 'octadecagon'
It is 18 diagonals
The formula for the number of diagonals (that is, lines joining non-adjacent vertices) belonging to any shape is n(n-3)/2. Therefore, an eighteen-sided polygon has 18 x (18 - 3)/2 = 135 diagonals.
If you say this shape is 18 sided i would guess it has 18 sides. ;)
It is a 3-dimensional simply connected shape with 12 polygonal faces. That is it! It can have as few as 8 or as many as 20 faces, as few as 18 or as many as 30 edges, the faces can all be triangles or the shape can have an endecagonal (11-sided) face. It can have between 9 and 170 diagonals.
All I can tell you is that a 16 sided shape is called a Hexadecagon
Well, darling, an 18-sided shape is called an octadecagon. It's a mouthful to say, but hey, at least now you can impress your friends with your geometry knowledge. Just don't ask me to draw one, honey, I'm not an artist.
no
Tetrahaidecahedron
octadecagon
enneadecagon or enneakaidecagon
An 18 sided shape is called a octadecagon. This refers to both 2 dimensional and 3 dimensional shapes in a mathematical sense.
153 diagonals.