begin
definition
let IT be ( ( ) ( )
set ) ;
end;
definition
let IT be ( ( ) ( )
set ) ;
end;
theorem
for
A being ( ( ) ( )
set ) holds
(
A : ( ( ) ( )
set ) is
preBoolean iff for
X,
Y being ( ( ) ( )
set ) st
X : ( ( ) ( )
set )
in A : ( ( ) ( )
set ) &
Y : ( ( ) ( )
set )
in A : ( ( ) ( )
set ) holds
(
X : ( ( ) ( )
set )
\/ Y : ( ( ) ( )
set ) : ( ( ) ( )
set )
in A : ( ( ) ( )
set ) &
X : ( ( ) ( )
set )
\ Y : ( ( ) ( )
set ) : ( ( ) ( )
Element of
bool b2 : ( ( ) ( )
set ) : ( ( ) ( non
empty )
set ) )
in A : ( ( ) ( )
set ) ) ) ;
registration
let A be ( ( ) ( )
set ) ;
end;
definition
let A be ( ( ) ( )
set ) ;
end;
registration
let A be ( ( ) ( )
set ) ;
end;
registration
let A be ( ( ) ( )
set ) ;
end;