reserve I for set;
reserve S for non empty non void ManySortedSign,
  U0, U1 for non-empty MSAlgebra over S;
reserve s for SortSymbol of S;
reserve e for Element of (Equations S).s;
reserve E for EqualSet of S;

theorem Th29:
  e`1 in (the Sorts of TermAlg S).s
proof
  set T = the Sorts of TermAlg S;
  e is Element of [:T.s, T.s:] by PBOOLE:def 16;
  hence thesis by MCART_1:10;
end;
