Pyramid Corners

Date: 05/01/2001 at 18:07:01
From: Mrs. Beauchamp's class
Subject: Pyramids

How many corners does a pyramid have? We have found that the point is 
called a vertex, but is this considered a corner?

Date: 05/06/2001 at 14:01:17
From: Doctor Douglas
Subject: Re: Pyramids

Hi everyone,

A square pyramid (one that has a square base) has five vertices. If 
the pyramid has a triangular base, then it is called a "tetrahedron" 
and has only four vertices.

Mathematicians prefer the word "vertex" because it is more *precise* 
than the word "corner." For example, we often think that a room has 
four corners because we are referring to the four vertical edges 
rather than the eight vertices. If this were the definition of 
"corner" that we are supposed to use for the square pyramid, then it 
would have four corners (and five vertices).

I hope this helps. Please write back if you'd like to discuss this 
some more, or if you have other questions.

- Doctor Douglas, The Math Forum
  http://mathforum.org/dr.math/