theorem
  not K is being_line implies Plane(K,P) = {}
proof
  assume
A1: not K is being_line;
  set x = the Element of Plane(K,P);
  assume Plane(K,P)<>{};
  then x in Plane(K,P);
  then ex a st x=a & ex b st a,b // K & b in P;
  hence contradiction by A1,AFF_1:26;
end;
