begin
registration
let X be ( ( ) ( )
set ) ;
end;
theorem
for
X being ( ( ) ( )
set )
for
Y being ( ( ) ( )
Subset of ) holds
(
Y : ( ( ) ( )
Subset of ) is
lower iff for
x,
y being ( ( ) ( )
set ) st
x : ( ( ) ( )
set )
c= y : ( ( ) ( )
set ) &
y : ( ( ) ( )
set )
in Y : ( ( ) ( )
Subset of ) holds
x : ( ( ) ( )
set )
in Y : ( ( ) ( )
Subset of ) ) ;
theorem
for
X being ( ( ) ( )
set )
for
Y being ( ( ) ( )
Subset of ) holds
(
Y : ( ( ) ( )
Subset of ) is
upper iff for
x,
y being ( ( ) ( )
set ) st
x : ( ( ) ( )
set )
c= y : ( ( ) ( )
set ) &
y : ( ( ) ( )
set )
c= X : ( ( ) ( )
set ) &
x : ( ( ) ( )
set )
in Y : ( ( ) ( )
Subset of ) holds
y : ( ( ) ( )
set )
in Y : ( ( ) ( )
Subset of ) ) ;
begin
begin
begin