In the diagram of circle O, tangent PB is drawn as is secant PAC. We wish to prove the Secant/Tangent Length Theorem, i. e. PA x PC = PB^2. (a) Explain why PAB is similar to ΔPBC (i. e. explain which two angles pairs must be congruent and why).
(b) Set up a proportion involving PA, PB, PC, and based on the similar triangles and rewrite it in product form. Draw the two similar triangle separately and in the same orientation to help.