theorem Th9:
  for A being disjoint_valued non-empty MSAlgebra over S
  for B being non-empty MSAlgebra over S
  for f being ManySortedFunction of A,B
  for a being Element of (the Sorts of A).s holds f.a = f.s.a
  proof
    let A be disjoint_valued non-empty MSAlgebra over S;
    let B be non-empty MSAlgebra over S;
    let f be ManySortedFunction of A,B;
    let a be Element of (the Sorts of A).s;
    thus f.a = f.(the_sort_of a).a  by ABBR .= f.s.a  by SORT;
  end;
