Types of Pyramids
Date: 06/08/99 at 00:21:07 From: Rhiannon Lipman Subject: Mathematical Pyramids What are the types of pyramids? I know that a pyramid with a base that has four equal sides is a square pyramid, but what are the other types called and what do they look like?
Date: 06/08/99 at 01:29:58 From: Doctor Barrus Subject: Re: Mathematical Pyramids Hi, Rhiannon! Good question! You're right - a pyramid with a base that is square is called a square pyramid. Most other pyramids are called by the name of their base. So, for example, a pyramid whose base has five equal sides (in other words, whose base is a regular pentagon) is called a pentagonal pyramid. A 6-sided (hexagon) base pyramid is called a hexagonal pyramid, a 7-sided (heptagon) one is called a heptagonal pyramid, etc. There's one pretty important exception to that rule. It's the pyramid whose base is an equilateral triangle - a triangle with 3 equal sides. If the sides of the pyramid that go up from the base to the top of the pyramid are all this same length, too, then the pyramid is called a tetrahedron. This is an important pyramid. It has 6 edges, all of the same length, and 4 sides that are all exactly the same shape! It's been known for thousands of years. For a picture of a tetrahedron, see the Dr. Math FAQ: http://mathforum.org/dr.math/faq/formulas/faq.polyhedron.html#tetrahedron or Peter T. Wang's Platonic Solids page: http://www.ugcs.caltech.edu/~peterw/studies/platonic/tetrahedron.html I hope this is clear and has helped. Good luck! - Doctor Barrus, The Math Forum http://mathforum.org/dr.math/
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