The Angular Frequency of a Physical Pendulum equation calculates the approximate value of the angular frequency given that the amplitude of the pendulum is small.

Reference

Young, Hugh and Freeman, Roger.  University Physics With Modern Physics.  Addison-Wesley, 2008. 12th Edition, (ISBN-13: 978-0321500625 ISBN-10: 0321500628 ) Pg 438, eq 13.38