let P be Subset of (TOP-REAL 2); :: thesis: ( (NW-corner P) `2 = (N-min P) `2 & (NW-corner P) `2 = (N-max P) `2 & (N-min P) `2 = (N-max P) `2 & (N-min P) `2 = (NE-corner P) `2 & (N-max P) `2 = (NE-corner P) `2 )
( (N-min P) `2 = N-bound P & (N-max P) `2 = N-bound P ) by EUCLID:52;
hence ( (NW-corner P) `2 = (N-min P) `2 & (NW-corner P) `2 = (N-max P) `2 & (N-min P) `2 = (N-max P) `2 & (N-min P) `2 = (NE-corner P) `2 & (N-max P) `2 = (NE-corner P) `2 ) by EUCLID:52; :: thesis: verum