CAMBRIDGE, MA–MIT mathematics professor Dr. Charles J. Chang has had the Pythagorean Theorem, a popular mathematical equation, running through his head all day, he reported Monday. "I overheard one of my colleagues discussing it with a student this morning, and ever since, I haven't been able to shake the damn thing," Chang said of the simple theorem, which is used to calculate the hypotenuse of a right triangle. "The weird thing is, I'm not even all that into Pythagoras–I mainly read Boolean and Quadratic–but it's just so catchy." Chang has made numerous attempts to get the theorem out of his head, including reading all of E.H. Spanier's Algebraic Topology and calculating the circumferences of various circles.