reserve IPP for IncProjSp;
reserve a,b,c,d,p,q,o,r,s,t,u,v,w,x,y for POINT of IPP;
reserve A,B,C,D,L,P,Q,S for LINE of IPP;

theorem Th8:
  ex c st c on A & c <>a & c <>b
proof
  consider p,q,r such that
A1: p<>q & q<>r & r<>p and
A2: p on A & q on A & r on A by INCPROJ:def 7;
  p<>a & p<>b or q<>a & q<>b or r<>a & r<>b by A1;
  hence thesis by A2;
end;
