I found condition when circle is drawn in wrong place and size (file "problem_a.dxf") or I cannot draw that circle (file "problem_b.dxf").
What I want: circle which is tangential to three lines and which is placed at left side of lines.
Linux 3.11.0-13-generic 64bit Kubuntu 13.10
SCM Revision: 2.0.0rc2
Compiler: GNU GCC 4.8.1
Qt Version: 4.8.4
Compiled on: Sep 17 2013