theorem
  (exp((th*<i>)))*'=exp(-(th*<i>))
proof
 (exp((th*<i>)))*'=(Sum((th*<i>) ExpSeq))*' by Def14
    .=Sum((-(th*<i>)) ExpSeq) by Lm4
    .=exp(-(th*<i>)) by Def14;
  hence thesis;
end;
