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Difference between revisions of "Barbier theorem"

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''on curves of constant width''
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''on [[Constant width, curve of|curves of constant width]]''
  
If the distance between any two parallel supporting straight lines to a curve is constant and equal to <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/b/b015/b015240/b0152401.png" />, then the length of the curve is <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/b/b015/b015240/b0152402.png" />. Discovered by E. Barbier in 1860.
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If the distance between any two parallel supporting straight lines to a curve is constant and equal to $a$, then the length of the curve is $\pi a$. Discovered by E. Barbier in 1860.
  
  
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====References====
 
====References====
<table><TR><TD valign="top">[a1]</TD> <TD valign="top">  E. Barbier,  "Note sur le problème de l'ainguille et le jeu du joint couvert"  ''J. Math. Pure Appl.'' , '''5'''  (1860)  pp. 273–286</TD></TR><TR><TD valign="top">[a2]</TD> <TD valign="top">  T. Bonnesen,  W. Fenchel,  "Theorie der konvexen Körper" , Springer  (1934)</TD></TR></table>
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<table>
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<TR><TD valign="top">[a1]</TD> <TD valign="top">  E. Barbier,  "Note sur le problème de l'ainguille et le jeu du joint couvert"  ''J. Math. Pure Appl.'' , '''5'''  (1860)  pp. 273–286</TD></TR>
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<TR><TD valign="top">[a2]</TD> <TD valign="top">  T. Bonnesen,  W. Fenchel,  "Theorie der konvexen Körper" , Springer  (1934)</TD></TR>
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</table>

Latest revision as of 17:28, 10 October 2016

on curves of constant width

If the distance between any two parallel supporting straight lines to a curve is constant and equal to $a$, then the length of the curve is $\pi a$. Discovered by E. Barbier in 1860.


Comments

The original work of E. Barbier is [a1].

References

[a1] E. Barbier, "Note sur le problème de l'ainguille et le jeu du joint couvert" J. Math. Pure Appl. , 5 (1860) pp. 273–286
[a2] T. Bonnesen, W. Fenchel, "Theorie der konvexen Körper" , Springer (1934)
How to Cite This Entry:
Barbier theorem. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Barbier_theorem&oldid=17513
This article was adapted from an original article by A.B. Ivanov (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article