9.47 A direct-coupled amplifier has a dominant pole at
1000 rad/s and three coincident poles at a much higher frequency.
These nondominant poles cause the phase lag of the
amplifier at high frequencies to exceed the 90° angle due to the
dominant pole. It is required to limit the excess phase at ω = 107
rad/s to 30° (i.e., to limit the total phase angle to −120°). Find
the corresponding frequency of the nondominant poles.