Remark that the exponential and logarithmic function of the same base are symmetric to the bisector line of the first quadrant, y=x. Note the symmetry of the exponential function base [b]a[/b] and [b]1/a[/b] related to the y-axis, moreover for the logarithmic function of base [b]a[/b] and [b]1/a[/b] related to the x-axis. The complex of the four functions is visualised here and helps studying them.