[pstricks] how to use draw a circle of radius \sqrt{2} without using a calculator

[Luiz Fernando C Camargo]

Hello,

I know things like this

   \SpecialCoor
   \pscircle(!2 sqrt 2 mul 1){3}

Fine, but I can't figure out how to draw, say, a circle of center
(0,0) and radius \sqrt{2} without using a calculator. Is there an
easy way?

Thank you,

Luiz Fernando