If youre a teacher and youre reading this I just want to say, good job and you should tell all of your students to subscribe. Another thing, on twitter people have . br brDaphne Koller is enticing top universities to put their most intriguing courses online for free -- not just as a service, but as a way to research how people learn. br br On any given day were lied to from 10 to 200 times, and the clues to detect those lie can be subtle and counter-intuitive. Pamela Meyer . br brFinding the slope of a tangent line to a curve (the derivative). Introduction to Calculus. Watch the next lesson: .