[pstricks] Tracing angles between two lines defined by nodes

[Christoph Bersch]

Agostino De Marco schrieb:
> 
> if I have three nodes, say C, P1 and P2,
> I can think of two lines, departing from C,  "line 1" connecting C to P1,
> the other "line 2" connecting C to P2.
> My question is this:
> How can I draw an arc, centered in C, going from line 1 to line 2
> indicating the angle between them ?

You can use the pst-eucl package:

\documentclass{article}
\usepackage{pst-eucl}

\begin{document}
\begin{pspicture}[showgrid=true](4,5)
   \pstGeonode(0,0){C}(4,1){P1}(3,5){P2}
   \psline(P1)(C)(P2)
   \pstMarkAngle[arrows=->, MarkAngleRadius=1, linecolor=red]{P1}{C}{P2}{}
\end{pspicture}
\end{document}

Instead of \pstGeonode you can of course also use \pnode to define the 
nodes.

Christoph