reserve x,y for set;
reserve X for non empty set;
reserve a,b,c,d for Element of X;
reserve S for OAffinSpace;
reserve a,b,c,d,p,q,r,x,y,z,t,u,w for Element of S;

theorem Th26:
  ex t st x,y '||' z,t & x,z '||' y,t
proof
  consider t such that
A1: x,y // z,t & x,z // y,t and
  y<>t by ANALOAF:def 5;
  x,y '||' z,t & x,z '||' y,t by A1;
  hence thesis;
end;
