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Name: 90 = 100: A Proof
ID: m12727
Language: English (en)
Summary: A (purported) geometric proof that 90=100.
Subject: Science and Technology
Keywords: 0 = 1, 90 = 100, false, geometry, paradox, proof
Document Type: -//CNX//DTD CNXML 0.5 plus MathML//EN
License: Creative Commons Attribution License CC-BY 2.0
Authors: Ian Barland (ibarland@radford.edu), Moshe Vardi (vardi@cs.rice.edu), Phokion Kolaitis (kolaitis@cse.ucsc.edu), Matthias Felleisen (matthias@ccs.neu.edu), John Greiner (greiner@cs.rice.edu)
Copyright Holders: Ian Barland (ibarland@radford.edu), Moshe Vardi (vardi@cs.rice.edu), Phokion Kolaitis (kolaitis@cse.ucsc.edu), Matthias Felleisen (matthias@ccs.neu.edu), John Greiner (greiner@cs.rice.edu)
Maintainers: Ian Barland (ibarland@radford.edu), John Greiner (greiner@cs.rice.edu)
Latest version: 1.8 (history)
First publication date: Mar 14, 2005 11:12 am US/Central
Last revision to module: Apr 7, 2007 6:09 pm GMT-5
Module XML: m12727_1.8.cnxml

Version History

Version: 1.8 Apr 7, 2007 6:09 pm GMT-5 by Ian Barland
Changes: 
Change justification#2 to mention AD (rather than BC).

Somehow the post-proof discussion got lost; restored that.
Version: 1.7 Jan 11, 2007 2:22 pm US/Central by John Greiner
Changes: 
Fixed typos in proof.
Version: 1.6 Jun 16, 2006 11:43 am GMT-5 by Ian Barland
Changes: 
Point out the the tiny steps aren't included in informal proofs, but will be for a while here.
Version: 1.5 Jan 13, 2006 3:43 pm US/Central by Ian Barland
Changes: 
Added greiner as maintainer/author, ...
Version: 1.4 Jan 11, 2006 2:34 pm US/Central by Ian Barland
Changes: 
Fixed wrong names of bisectors; 
clarified "SSS"; made justifications 
into sentence (frags).
Version: 1.3 Dec 2, 2005 1:55 pm US/Central by Ian Barland
Changes: 
Fix an angle-name, and a markupo.
Version: 1.2 Jul 15, 2005 2:16 pm GMT-5 by Ian Barland
Changes: 
Fix line numbers (due to a non-
proof line still being numbered, in 
cnxml).
Version: 1.1 Mar 21, 2005 5:21 pm US/Central by Ian Barland
Changes: 
Initial publish.

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How to Cite and Attribute This Content

The following citation styles comply with the attribution requirements for the license (CC-BY 2.0) of this work:

American Chemical Society (ACS) Style Guide:

Barland, I.; Vardi, M.; Kolaitis, P.; Felleisen, M.; Greiner, J. 90 = 100: A Proof, Connexions Web site. http://cnx.org/content/m12727/1.8/, Apr 7, 2007.

American Medical Assocation (AMA) Manual of Style:

Barland I, Vardi M, Kolaitis P, Felleisen M, Greiner J. 90 = 100: A Proof [Connexions Web site]. April 7, 2007. Available at: http://cnx.org/content/m12727/1.8/.

American Psychological Assocation (APA) Publication Manual:

Barland, I., Vardi, M., Kolaitis, P., Felleisen, M., & Greiner, J. (2007, April 7). 90 = 100: A Proof. Retrieved from the Connexions Web site: http://cnx.org/content/m12727/1.8/

Chicago Manual of Style (Bibliography):

Barland, Ian, Moshe Vardi, Phokion Kolaitis, Matthias Felleisen, and John Greiner. "90 = 100: A Proof." Connexions. April 7, 2007. http://cnx.org/content/m12727/1.8/.

Chicago Manual of Style (Note):

Ian Barland and others, "90 = 100: A Proof," Connexions, April 7, 2007, http://cnx.org/content/m12727/1.8/.

Chicago Manual of Style (Reference, in Author-Date style):

Barland, I., Vardi, M., Kolaitis, P., Felleisen, M., & Greiner, J. 2007. 90 = 100: A Proof. Connexions, April 7, 2007. http://cnx.org/content/m12727/1.8/.

Modern Languages Association (MLA) Style Manual:

Barland, Ian, Moshe Vardi, Phokion Kolaitis, Matthias Felleisen, and John Greiner. 90 = 100: A Proof. Connexions. 7 Apr. 2007 <http://cnx.org/content/m12727/1.8/>.