reserve F for Field;
reserve S for OrtSp of F;
reserve a,b,c,d,p,q,r,x,y,z for Element of S;
reserve k,l for Element of F;

theorem Th19:
  not b _|_ a implies ProJ(a,b,b) = 1_F
proof
A1: b-b = 0.S by RLVECT_1:5;
  assume not b _|_ a;
  hence thesis by A1,Th1,Th18;
end;
