[pstricks] radius of a circle

[mathias legrand]

Hi all,

what is your technique to indicate the radius of a circle with pstricks?

I have something like:

\documentclass{article}
\usepackage{pstricks-add}
\begin{document}
\begin{pspicture}(-4,-4)(4,4)
\pscircle(0,0){4}
\cnode*(0,0){0pt}{A}
\cnode*(4,2){0pt}{B}
\ncline[nodesep=3pt]{<->}{A}{B}
\mput*{$R$}
\end{pspicture}
\end{document}

but I would like to be able to parametrize the B node position with some 
postscript command
such as:

\cnode*(4*cos(62),4*sin(62)){0pt}{B} (for instance)

Thanks for your lights.

Mathias