let p, q, r, s be ext-real number ; :: thesis: ( p < q & ].p,q.] = ].r,s.] implies ( p = r & q = s ) )
assume that
A1:
p < q
and
A2:
].p,q.] = ].r,s.]
; :: thesis: ( p = r & q = s )
A3:
( r <= p & q <= s )
by A1, A2, Th61;
then
r < q
by A1, XXREAL_0:2;
then
r < s
by A3, XXREAL_0:2;
then
( p <= r & s <= q )
by A2, Th61;
hence
( p = r & q = s )
by A3, XXREAL_0:1; :: thesis: verum