POWER THEOREM | Grade 10 Math | JERRYCO JAURIGUE
For a given point and circle, the product of the lengths of the whole segments from the point to the circle is constant along any line through the point and circle.
Reference
Prentice Hall Mathematics | Geometry | Teacher's Edition
Kennedy, D., Charles, R., Hall, B., McNemar, B., Ramirez, A., Bellman, A. and Bass, L., 2007. Prentice Hall mathematics. Boston, Mass.: Pearson, Prentice Hall.