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
Tetrahaidecahedron
octadecagon
enneadecagon or enneakaidecagon
no
An 18 sided shape is called a octadecagon. This refers to both 2 dimensional and 3 dimensional shapes in a mathematical sense.
153 diagonals.
Octadecadron