Hey Mr. Odden! I just wanted to ask what kind of software/presentation software you use to communicate mathematics through these videos? Thanks for making these.
Hi Alex. The presentations are done with Keynote on a Mac. I use LaTeXit to create the equations, and I have loaded special CMU (Computer Modern Unicode) fonts onto my system for consistency with the math typesetting. The screencast is done using ScreenFlow and I use a YetiBlue microphone with a pop screen.
So sorry for the delay! By definition, D is *always* positive. (In the video I used the distance formula to find an expression for D^2; since D represents a DISTANCE we simply take the positive square root to define D.) The upshot is that D>0 for all points on the circle.
