reserve x for set,
  p,q,r,s,t,u for ExtReal,
  g for Real,
  a for Element of ExtREAL;

theorem Th226:
  p in REAL implies [.p,q.[ c= REAL
proof
  assume
A1: p in REAL;
  let x be ExtReal;
  assume
A2: x in [.p,q.[;
  then
A3: p <= x by Th3;
  x < q by A2,Th3;
  hence thesis by A1,A3,XXREAL_0:46;
end;
