theorem Th96:
  x, u ==>* y, TS implies x, u^v ==>* y, v, TS
proof
  assume x, u ==>* y, TS;
  then x, u ==>* y, <%>E, TS;
  then x, u^v ==>* y, {}^v, TS by Th86;
  hence thesis;
end;
