Prolate Cycloid Evolute

$\begin{figure}\begin{center}\BoxedEPSF{ProlateCycloidEvolute.epsf scaled 700}\end{center}\end{figure}$

The Evolute of the Prolate Cycloid is given by

$\displaystyle x$	$\textstyle =$	$\displaystyle {a[-2b\phi+2a\phi\cos\phi-2a\sin\phi+b\sin(2\phi)]\over 2(a\cos\phi-b)}$
$\displaystyle y$	$\textstyle =$	$\displaystyle {a(a-b\cos\phi)^2\over b(a\cos\phi-b)}.$