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Difference between revisions of "Cornu spiral"

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A transcendental plane curve (see Fig.) whose natural equation is
 
A transcendental plane curve (see Fig.) whose natural equation is
  
<table class="eq" style="width:100%;"> <tr><td valign="top" style="width:94%;text-align:center;"><img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/c/c026/c026510/c0265101.png" /></td> </tr></table>
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$$r=\frac as,$$
  
where <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/c/c026/c026510/c0265102.png" /> is the radius of curvature, <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/c/c026/c026510/c0265103.png" /> and <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/c/c026/c026510/c0265104.png" /> is the arc length. It can be parametrized by the [[Fresnel integrals|Fresnel integrals]]
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where $r$ is the radius of curvature, $a=\text{const}$ and $s$ is the arc length. It can be parametrized by the [[Fresnel integrals|Fresnel integrals]]
  
<table class="eq" style="width:100%;"> <tr><td valign="top" style="width:94%;text-align:center;"><img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/c/c026/c026510/c0265105.png" /></td> </tr></table>
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$$x=\int\limits_0^t\cos\frac{s^2}{2a}ds,\quad y=\int\limits_0^t\sin\frac{s^2}{2a}ds,$$
  
which are well-known in diffraction theory. The spiral of Cornu touches the horizontal axis at the origin. The asymptotic points are <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/c/c026/c026510/c0265106.png" /> and <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/c/c026/c026510/c0265107.png" />.
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which are well-known in diffraction theory. The spiral of Cornu touches the horizontal axis at the origin. The asymptotic points are $M_1(\sqrt{\pi a}/2,\sqrt{\pi a}/2)$ and $M_1(-\sqrt{\pi a}/2,-\sqrt{\pi a}/2)$.
  
 
<img style="border:1px solid;" src="https://www.encyclopediaofmath.org/legacyimages/common_img/c026510a.gif" />
 
<img style="border:1px solid;" src="https://www.encyclopediaofmath.org/legacyimages/common_img/c026510a.gif" />

Revision as of 11:39, 26 July 2014

clothoid

A transcendental plane curve (see Fig.) whose natural equation is

$$r=\frac as,$$

where $r$ is the radius of curvature, $a=\text{const}$ and $s$ is the arc length. It can be parametrized by the Fresnel integrals

$$x=\int\limits_0^t\cos\frac{s^2}{2a}ds,\quad y=\int\limits_0^t\sin\frac{s^2}{2a}ds,$$

which are well-known in diffraction theory. The spiral of Cornu touches the horizontal axis at the origin. The asymptotic points are $M_1(\sqrt{\pi a}/2,\sqrt{\pi a}/2)$ and $M_1(-\sqrt{\pi a}/2,-\sqrt{\pi a}/2)$.

Figure: c026510a

The spiral of Cornu is sometimes called the spiral of Euler after L. Euler, who mentioned it first (1744). Beginning with the works of A. Cornu (1874), the spiral of Cornu is widely used in the calculation of diffraction of light.

References

[1] E. Jahnke, F. Emde, F. Lösch, "Tafeln höheren Funktionen" , Teubner (1966)


Comments

References

[a1] J.D. Lawrence, "A catalog of special plane curves" , Dover, reprint (1972)
How to Cite This Entry:
Cornu spiral. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Cornu_spiral&oldid=32541
This article was adapted from an original article by D.D. Sokolov (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article