# [pstricks] It might be a bug in finding angle

Counter Terrorist the.counterterrorist at yahoo.com
Sat Jul 28 09:03:09 CEST 2012

Dear Luis,

I still don't understand why the arc center becomes (6,6) for the second example but it is (3,3) in for the first example.
In my understanding, if \pnode(3,3){O} then \psarcn[origin={O}](O)... should be identical to the following:

* \psarcn[origin={O}](3,3)...

* \psarcn[origin={3,3}](O)...
* \psarcn[origin={3,3}](3,3)...

I have not found the details in PSTricks manual how PSTricks makes assumption and calculates the arc center if nodes and literal numbers are specified.

Thank you.

Higgs Boson

Date: Mon, 23 Jul 2012 11:34:15 +0100
From: Luis Sequeira <lfsequeira at gmail.com>

There is a bug in your code...

In the second version, you have

\psarcn[origin={O},linecolor=red]{->}(3,3) ....

You set the origin at (O), which has coordinates (3,3) so now your center (3,3) is actually at (3,3)+(3,3), as appears in the picture.

You should write just

\psarcn[linecolor=red]{->}(3,3) ....

or (perhaps better, since it retains the fact that your coordinates are relative to (O)):

\psarcn[origin={O},linecolor=red]{->}(0,0) ....

Luis Sequeira

Date: Sat, 21 Jul 2012 17:52:52 -0700
From: Counter Terrorist <the.counterterrorist at yahoo.com>

Dear Mr. Herbert,

I found a bug in PSTricks.?

Even though the points (O) and (3,3) represent the same point,
the second pspicture produces an arc at a wrong pivot.?

\documentclass[pstricks,border=1cm]{standalone}
\usepackage{pst-eucl}

\begin{document}

\begin{pspicture}[showgrid=top](9,8)
\pstGeonode(3,3){O}(5,5){A}(5,1){B}
\pscircle[linestyle=dashed](O){2}
\psarcn[origin={O},linecolor=red]{->}
(O)%<=============== COMPARE THIS ONE
{2}{(A)}{(B)}
\psline(A)(O)(B)
\end{pspicture}?

\begin{pspicture}[showgrid=top](9,8)
\pstGeonode(3,3){O}(5,5){A}(5,1){B}
\pscircle[linestyle=dashed](O){2}
\psarcn[origin={O},linecolor=red]{->}
(3,3)%<================ WITH THIS ONE
{2}{(A)}{(B)}
\psline(A)(O)(B)
\end{pspicture}?

\end{document}