⁹ The practice of signifying the end of a mathematical proof with the initials Q.E.D.—“quod erat demonstrandum,” or, “which was to be demonstrated”—goes back many centuries, and is in fact a translation of a Greek phrase used by Euclid and Archimedes to signify the same thing. It’s fallen a bit out of fashion among mathematicians lately, but we, being humanists at heart, like a bit of old-fashioned Latin now and again.