theorem
  x0>0 & x1>0 implies
  log(number_e,x0) + log(number_e,x1) = log(number_e,x0*x1)
proof
  assume
A1:x0>0 & x1>0;
  number_e > 1 by TAYLOR_1:11,XXREAL_0:2;
  hence thesis by A1,POWER:53;
end;
