let f1, f2 be BinOp of REAL ; ( ( for x, y being Real holds f1 . x,y = max x,y ) & ( for x, y being Real holds f2 . x,y = max x,y ) implies f1 = f2 )
assume that
A3:
for x, y being Real holds f1 . x,y = max x,y
and
A4:
for x, y being Real holds f2 . x,y = max x,y
; f1 = f2
for x, y being Element of REAL holds f1 . x,y = f2 . x,y
hence
f1 = f2
by BINOP_1:2; verum