A square-pyramid
h
Five.
octagonal based pyramid
octagonal pyramid
If you imagine a square-based pyramid sitting on its base, there will be the four corners of the square, plus the top: a square-based pyramid has five corners.
Yes.
Use the Pythagorean theorem (a-squared + b-squared = c-squared) Remember, the hypotenuse is c.
A nonagon based pyramid.
An icosagonal based pyramid.
It will be a square shape if it is a squared based pyramid
A tetrahedron.
Triangular Pyramid, Squared Pyramid, Pyramid