let I be non empty set ; :: thesis: for M being ManySortedSet of I holds id M is Equivalence_Relation of M
let M be ManySortedSet of I; :: thesis: id M is Equivalence_Relation of M
set J = id M;
for i being set st i in I holds
(id M) . i is Relation of (M . i)
proof
let i be set ; :: thesis: ( i in I implies (id M) . i is Relation of (M . i) )
assume i in I ; :: thesis: (id M) . i is Relation of (M . i)
then (id M) . i = id (M . i) by MSUALG_3:def 1;
hence (id M) . i is Relation of (M . i) ; :: thesis: verum
end;
then reconsider J = id M as ManySortedRelation of M by MSUALG_4:def 1;
for i being set
for R being Relation of (M . i) st i in I & J . i = R holds
R is Equivalence_Relation of (M . i)
proof
let i be set ; :: thesis: for R being Relation of (M . i) st i in I & J . i = R holds
R is Equivalence_Relation of (M . i)

let R be Relation of (M . i); :: thesis: ( i in I & J . i = R implies R is Equivalence_Relation of (M . i) )
assume that
A1: i in I and
A2: J . i = R ; :: thesis: R is Equivalence_Relation of (M . i)
J . i = id (M . i) by ;
hence R is Equivalence_Relation of (M . i) by ; :: thesis: verum
end;
hence id M is Equivalence_Relation of M by MSUALG_4:def 2; :: thesis: verum