View source for Si-ci-spiral

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A plane curve whose equation in rectangular Cartesian coordinates $(x,y)$ has the form

$$x=\operatorname{ci}(t),\quad y=\operatorname{si}(t),$$

where $\operatorname{ci}$ is the [[Integral cosine|integral cosine]], $\operatorname{si}$ is the [[Integral sine|integral sine]] and $t$ is a real parameter (see Fig.).

<img style="border:1px solid;" src="https://www.encyclopediaofmath.org/legacyimages/common_img/s084980a.gif" />

Figure: s084980a

The arc length from $t=0$ to $t=t_0$ is equal to $\log t_0$, and the curvature is equal to $\kappa=t_0$.

====References====
<table><TR><TD valign="top">[1]</TD> <TD valign="top">  E. Jahnke,   F. Emde,   F. Lösch,   "Tafeln höheren Funktionen" , Teubner  (1966)</TD></TR>
<TR><TD valign="top">[a1]</TD> <TD valign="top">  M. Abramowitz,   I.A. Stegun,   "Handbook of mathematical functions" , Dover, reprint  (1972)</TD></TR></table>

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