let X be set ; :: thesis: for L being non empty ZeroStr holds (0. L) | (X,L) = 0_ (X,L)
let L be non empty ZeroStr ; :: thesis: (0. L) | (X,L) = 0_ (X,L)
set o1 = (0. L) | (X,L);
set o2 = 0_ (X,L);

A1: now

set m = (0_ (X,L)) +* ((EmptyBag X),(0. L));
let x be set ; :: thesis: ( x in Bags X implies ((0. L) | (X,L)) . b₁ = (0_ (X,L)) . b₁ )
reconsider m = (0_ (X,L)) +* ((EmptyBag X),(0. L)) as Function of (Bags X), the carrier of L ;
reconsider m = m as Function of (Bags X),L ;
reconsider m = m as Series of X,L ;
assume x in Bags X ; :: thesis: ((0. L) | (X,L)) . b₁ = (0_ (X,L)) . b₁
then reconsider x9 = x as bag of X ;
A2: dom (0_ (X,L)) = dom ((Bags X) --> (0. L)) by POLYNOM1:def 7
.= Bags X by FUNCOP_1:13 ;
then A3: m = (0_ (X,L)) +* ((EmptyBag X) .--> (0. L)) by FUNCT_7:def 3;
A4: dom ((EmptyBag X) .--> (0. L)) = {(EmptyBag X)} by FUNCOP_1:13;
then A5: EmptyBag X in dom ((EmptyBag X) .--> (0. L)) by TARSKI:def 1;
A6: m . (EmptyBag X) = ((0_ (X,L)) +* ((EmptyBag X) .--> (0. L))) . (EmptyBag X) by A2, FUNCT_7:def 3
.= ((EmptyBag X) .--> (0. L)) . (EmptyBag X) by A5, FUNCT_4:13
.= 0. L by FUNCOP_1:72 ;

per cases ( x9 = EmptyBag X or x9 <> EmptyBag X ) ;

suppose x9 = EmptyBag X ; :: thesis: ((0. L) | (X,L)) . b₁ = (0_ (X,L)) . b₁

hence ((0. L) | (X,L)) . x = (0_ (X,L)) . x by A6, POLYNOM1:22; :: thesis: verum

end;

suppose x9 <> EmptyBag X ; :: thesis: ((0. L) | (X,L)) . b₁ = (0_ (X,L)) . b₁

then not x9 in dom ((EmptyBag X) .--> (0. L)) by A4, TARSKI:def 1;
hence ((0. L) | (X,L)) . x = (0_ (X,L)) . x by A3, FUNCT_4:11; :: thesis: verum

end;

end;

end;

( Bags X = dom ((0. L) | (X,L)) & Bags X = dom (0_ (X,L)) ) by FUNCT_2:def 1;
hence (0. L) | (X,L) = 0_ (X,L) by A1, FUNCT_1:2; :: thesis: verum