reserve S for non void non empty ManySortedSign,
  U1 for MSAlgebra over S,
  o for OperSymbol of S,
  s for SortSymbol of S;

theorem Th1:
  for R be MSEquivalence-like ManySortedRelation of U1 holds R.s is
  Equivalence_Relation of (the Sorts of U1).s
by Def3,Def2;
