a triangle.
It is a quadrilateral.
A nonagon is a nine-sided polygon.
It looks like a square with a triangle on top of it.
An octogon- like a stop sign
A polygon
The base would be an octagon, or an eight sided polygon.
it look like a fifty sided shape
Like this
see related link below to see the 20 sided polygon
It is a seven-sided polygon
polyhedron
The Pentagon.
a triangle.
It is a quadrilateral.
It looks like a circle
A nonagon is a nine-sided polygon.