Converted by
Mathematica
June 17, 2001
![[Graphics:../Images/Pratica7_gr_227.gif]](../Images/Pratica7_gr_227.gif)
![[Graphics:../Images/Pratica7_gr_228.gif]](../Images/Pratica7_gr_228.gif)
![[Graphics:../Images/Pratica7_gr_229.gif]](../Images/Pratica7_gr_229.gif)