Talk:Eccentricity (mathematics)

First image not accurate when e=0

When the eccentricity is zero, one obtains an (infinitely small) circle around the focus, or alternatively a directrix that is infinitely far away. The current picture suggest a circle (red with e=0) that is obviously wrong. — Preceding unsigned comment added by 212.25.6.56 (talk) 09:54, 9 May 2020 (UTC)

Equations

what about Eccentricity (orbit) ? there's other equation, which is wrong ?

Neither. They both describe the same geometrical object, but the orbit definition uses parameters more likely to be found in an orbital mechanics setting than in a mathematical one. I prefer the orbital mechanics version, since there's no variability in the equivalent of k (which, incidentally, isn't required to be zero in case of a parabola, since a parabola has effectively infinite major axis). 192.91.147.34 19:13, 28 September 2006 (UTC)

Contradiction

At the beginning of the article, it states that the eccentricity of a line is infinite, while later on, the section "Straight Line" says that the eccentricity of a line is 1. Is there a contradiction? Splintercellguy 22:50, 26 April 2006 (UTC)

See Wikipedia:Reference desk/Archives/Mathematics/2006 October 23. 21:13, 15 November 2006 (UTC)

Corrections

I have made some corrections, in particular moved the definition of the second eccentricity to the section on ellipses. This notion is not defined for the other conic sections. Its defining equations make naturally no sense for the other conic sections, and were removed. Ceroklis 19:16, 5 October 2007 (UTC)

Straight Line

If propose to delete any mention of the eccentricity of a straight line, for the simple reason that this concept is not defined and is not used in the mathematical literature.

There is a big difference between saying that the concept of eccentricity can be more a less reasonably extended to straight lines and saying that the eccentricity of a straight line is so and so.

The extension may be interesting but it is a piece of mathematical trivia, or even original research, and has thus no place here. Morana 23:53, 1 November 2007 (UTC)

Done Morana (talk) 03:54, 23 January 2008 (UTC)

Eccentricity Formula Notation

Instead of writing the eccentricity formula for an ellipse as ${\frac {\sqrt {a^{2}-b^{2}}}{a}}$, wouldn't it be more clear to write it as ${\sqrt {1-{\frac {b^{2}}{a^{2}}}}}$ (and the same for the hyperbola using the + sign). It is then immediately clear that the eccentricity is between zero and one for the ellipse and larger than one for the hyperbola. 194.105.120.80 (talk) 11:38, 7 October 2010 (UTC)

I made the changes - see also Talk:Conic section. DVdm (talk) 11:55, 7 October 2010 (UTC)