Harold gets Bear to eat his breakfast with the command "Eet je ontbijt", which is Dutch for "Eat your breakfast".
Pythagorean Identity states the relationship between sine and cosine, sin² theta + cos² theta = 1. (Theta being the measured angle.)
Euler's Identity defines itself, e^(i pi) = -1. e is Euler's number, approximately 2.71828 and i is Imaginary units which as the name implies do not exist, so the equation proves that multiplying two numbers by a number which every mathematical law says cannot not exist can equal -1.
It does not appear to have ever been meant to have any meaning or practical use.