Nielsen's Spiral

$\begin{figure}\begin{center}\BoxedEPSF{NielsensSpiral.epsf}\end{center}\end{figure}$

The Spiral with parametric equations

$\displaystyle x(t)$	$\textstyle =$	$\displaystyle a\mathop{\rm ci}\nolimits (t)$	(1)
$\displaystyle y(t)$	$\textstyle =$	$\displaystyle a\mathop{\rm si}\nolimits (t),$	(2)

where $\mathop{\rm ci}\nolimits (t)$ is the Cosine Integral and $\mathop{\rm si}\nolimits (t)$ is the Sine Integral. The Cesàro Equation is

$\begin{displaymath} \kappa={e^{s/a}\over a}. \end{displaymath}$

(3)

References