let X be set ; for f being PartFunc of REAL,REAL st f | X is Lipschitzian holds
f | X is uniformly_continuous
let f be PartFunc of REAL,REAL; ( f | X is Lipschitzian implies f | X is uniformly_continuous )
assume
f | X is Lipschitzian
; f | X is uniformly_continuous
then consider r being real number such that
A1:
0 < r
and
A2:
for x1, x2 being real number st x1 in dom (f | X) & x2 in dom (f | X) holds
abs ((f . x1) - (f . x2)) <= r * (abs (x1 - x2))
by FCONT_1:33;
now reconsider r =
r as
Real by XREAL_0:def 1;
let p be
Real;
( 0 < p implies ex s being Element of REAL st
( 0 < s & ( for x1, x2 being Real st x1 in dom (f | X) & x2 in dom (f | X) & abs (x1 - x2) < s holds
abs ((f . x1) - (f . x2)) < p ) ) )assume A3:
0 < p
;
ex s being Element of REAL st
( 0 < s & ( for x1, x2 being Real st x1 in dom (f | X) & x2 in dom (f | X) & abs (x1 - x2) < s holds
abs ((f . x1) - (f . x2)) < p ) )take s =
p / r;
( 0 < s & ( for x1, x2 being Real st x1 in dom (f | X) & x2 in dom (f | X) & abs (x1 - x2) < s holds
abs ((f . x1) - (f . x2)) < p ) )thus
0 < s
by A1, A3, XREAL_1:141;
for x1, x2 being Real st x1 in dom (f | X) & x2 in dom (f | X) & abs (x1 - x2) < s holds
abs ((f . x1) - (f . x2)) < plet x1,
x2 be
Real;
( x1 in dom (f | X) & x2 in dom (f | X) & abs (x1 - x2) < s implies abs ((f . x1) - (f . x2)) < p )assume that A4:
x1 in dom (f | X)
and A5:
x2 in dom (f | X)
and A6:
abs (x1 - x2) < s
;
abs ((f . x1) - (f . x2)) < pA7:
r * (abs (x1 - x2)) < s * r
by A1, A6, XREAL_1:70;
abs ((f . x1) - (f . x2)) <= r * (abs (x1 - x2))
by A2, A4, A5;
then
abs ((f . x1) - (f . x2)) < (p / r) * r
by A7, XXREAL_0:2;
hence
abs ((f . x1) - (f . x2)) < p
by A1, XCMPLX_1:88;
verum end;
hence
f | X is uniformly_continuous
by Th1; verum