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 Th7:
  ex a st a on A
proof
  consider a,b,c such that
  a<>b and
  b<>c and
  c <>a and
A1: a on A and
  b on A and
  c on A by INCPROJ:def 7;
  take a;
  thus thesis by A1;
end;
