
theorem
  for a,b being Real st 1 < a & 0 < b < 1 holds log(a,b) < 0
  proof
    let a,b be Real;
    assume that
A1: 1 < a and
A2: 0 < b < 1;
    log(a,1) = 0 by A1,POWER:51;
    hence thesis by A1,A2,POWER:57;
  end;
