theorem Th32:
  1_F+1_F<>0.F & not b _|_ a & x=0.S implies PProJ(a,b,x,y) = 0.F
proof
  assume that
A1: 1_F+1_F<>0.F & not b _|_ a and
A2: x=0.S;
  for p holds p _|_ a or p _|_ x by A2,Th1,Th2;
  hence thesis by A1,Def3;
end;
