[pstricks] Right angle symbol in a 2D Projection

[Michael Sharpe]

On Feb 7, 2009, at 3:17 PM, Juergen Gilg wrote:

> \psellipticarc{->}(0,1.4)(0.2,0.11){120}{420}

Perhaps it would be easier not to use \psellipticarc, for in general  
that will require further rotation. If you have a right angle AOB in  
three dimensions and a circular arc with center O, its projection on a  
two dimensional plane may thought of as the vector parametric curve AA  
cos t+BB sin t, 0\le t\le \pi/2, where AA and BB are the projections  
on the plane of points on OA, OB at equal distance from the origin.  
This should look better, as the tangents at the endpoints will have  
the correct directions.

Michael