Converted by
Mathematica
June 17, 2001
![[Graphics:../Images/Pratica7_gr_190.gif]](../Images/Pratica7_gr_190.gif)
![[Graphics:../Images/Pratica7_gr_191.gif]](../Images/Pratica7_gr_191.gif)
![[Graphics:../Images/Pratica7_gr_192.gif]](../Images/Pratica7_gr_192.gif)