One- and Two-sided Polygons
Date: 12/07/1999 at 15:56:45 From: Sue Subject: Polygons Dr. Math: You said that there are such things as monogons and digons - one-sided and two-sided polygons. What are they? None of my math teachers has heard of them. Please write back with a little diagram of each. Thank you.
Date: 12/07/1999 at 16:13:32 From: Doctor Rob Subject: Re: Polygons Thanks for writing to Ask Dr. Math, Sue. Since there is no such thing, it would be really hard to draw a diagram of either. The names are constructed by analogy with names of figures with more sides. Mono- means one, Di- means two, and Octa- means 8. Thus Octagon for an 8-sided figure would correspond to Digon for a 2-sided one (if it existed) or Monogon for a 1-sided one (if it existed). Actually, on the surface of a sphere, you *can* have such figures: a monogon is a hemisphere, and a digon is a spherical lune (see http://mathforum.org/dr.math/faq/formulas/faq.sphere.html#lune for pictures). Of course you have to replace straight lines with great circles on the sphere for the sides, but that is standard practice in spherical geometry and trigonometry. - Doctor Rob, The Math Forum http://mathforum.org/dr.math/
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