Where does David McCullough get his subtitle for Chapter 12?

David McCullough obtains his subtitle for Chapter 12, "Adventure by Trigonometry," from a comment Phillippe Banau-Varilla makes. Banau-Varilla notes that diplomacy is as difficult for some to understand as trigonometry. McCullough references this comment as he relates the story of how the U.S. shifts from negotiating with Columbia to readying secret support for an armed revolt in Panama.