sin(x), cos(x) and e^x go to a bar. sin(x) and cos(x) are out having a good time and partying it up, but e^x is sitting at the table by himself. son(x) goes ove to him and say "e^x get out there and have some fun! what are you doing?" e^x replies, "What's the point? If I integrate or differentiate I just stay the same."
(I love this joke.)
P.S. ("I seldom drink beer, but when I do is Dos Equis")