reserve r, s, t, g for Real,

          r3, r1, r2, q3, p3 for Real;
reserve T for TopStruct,
  f for RealMap of T;
reserve p for Point of TOP-REAL 2,
  P for Subset of TOP-REAL 2,
  Z for non empty Subset of TOP-REAL 2,
  X for non empty compact Subset of TOP-REAL 2;

theorem Th53:
  (SW-corner P)`2 = (S-min P)`2 & (SW-corner P)`2 = (S-max P)`2 &
  (S-min P)`2 = (S-max P)`2 & (S-min P)`2 = (SE-corner P)`2 & (S-max P)`2 = (
  SE-corner P)`2
proof
  (S-min P)`2 = S-bound P & (S-max P)`2 = S-bound P by EUCLID:52;
  hence thesis by EUCLID:52;
end;
