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January 28th, 2019, 12:31 AM  #1 
Senior Member Joined: Nov 2011 Posts: 250 Thanks: 3  Example of properties that the circle unit hasn't
What are the properties the unit circle hasn't, but that ellipses have?
Last edited by skipjack; January 28th, 2019 at 07:16 AM. 
January 28th, 2019, 01:17 AM  #2 
Senior Member Joined: Oct 2009 Posts: 784 Thanks: 280 
Since the unit circle IS an ellipse, you won't find any property that is common to all ellipses and not the unit circle.

January 28th, 2019, 07:20 AM  #3 
Global Moderator Joined: Dec 2006 Posts: 20,636 Thanks: 2081 
Perhaps "ellipses other than the unit circle" was intended.

January 28th, 2019, 07:25 AM  #4 
Senior Member Joined: Oct 2009 Posts: 784 Thanks: 280 
Perhaps.

January 28th, 2019, 11:15 AM  #5 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 14,415 Thanks: 1025  
January 28th, 2019, 12:30 PM  #6 
Global Moderator Joined: May 2007 Posts: 6,761 Thanks: 696 
An ellipse has two different axes. If a planet is in orbit around the sun and it is an ellipse, the sun is at a focus, not at the center. For a circle, there is only one focus at the center. Last edited by skipjack; January 28th, 2019 at 09:14 PM. 
January 28th, 2019, 12:38 PM  #7 
Senior Member Joined: May 2016 From: USA Posts: 1,310 Thanks: 551 
Uhm. Look it up. From Wikipedia https://en.wikipedia.org/wiki/Ellipse An ellipse is a curve in a plane surrounding two focal points such that the sum of the distances to the two focal points is constant for every point on the curve. As such, it is a generalization of a circle, which is a special type of an ellipse having both focal points at the same location. The shape of an ellipse (how "elongated" it is) is represented by its eccentricity, which for an ellipse can be any number from 0 (the limiting case of a circle) to arbitrarily close to but less than 1. So, an ellipse that is not a circle does not have a single focal point. Other differences, such as the lack of a radius and the presence of positive eccentricity, follow from the duality of focal points. 

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circle, hant, properties, unit 
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