theorem Th31:
  p in W-most Z implies p`1 = (W-min Z)`1 & (Z is compact implies
  (W-min Z)`2 <= p`2 & p`2 <= (W-max Z)`2)
proof
A1: (SW-corner Z)`1 = W-bound Z & (W-min Z)`1 = W-bound Z by EUCLID:52;
A2: (NW-corner Z)`1 = W-bound Z by EUCLID:52;
  assume
A3: p in W-most Z;
  then p in LSeg(SW-corner Z, NW-corner Z) by XBOOLE_0:def 4;
  hence p`1 = (W-min Z)`1 by A1,A2,GOBOARD7:5;
  assume Z is compact;
  then reconsider Z as non empty compact Subset of TOP-REAL 2;
  (W-min Z)`2 = lower_bound (proj2|W-most Z) &
  (W-max Z)`2 = upper_bound (proj2|W-most Z )
  by EUCLID:52;
  hence thesis by A3,Lm3;
end;
