A bunch of functions are gathered at a party. The function ex is sitting all by himself in a corner of the room. Sin x walks up and asks, "Why don't you integrate?". ex replies despondently, "It won't make any difference."
What is the value of a contour integral around Western Europe? Answer, zero - all the poles are in Eastern Europe.
How many mathematicians does it take to change a lightbulb? Answer, infinitely many. Mathematicians can't change lightbulbs.
(Made that one up myself – it's a bit lame)
A mathematician is drinking with his doctor buddy in a bar. The doctor says, "How's your blood pressure?" The mathematician says, "Great! 210 over 130." The doctor says, "You need to get that treated." The mathematician asks, "Why?" The doctor says, "Well, normal blood pressure is in the range 120 over 70." The mathematician smiles and says, "Don't they teach you guys anything in med school these days?" The doctors says, "Enough to know that 210..." The mathematician shatkes his head in disbelief. Gets out his calculator, punches in a few numbers and waves it in the doctor's face
120/70 = 1. 714
210/130 = 1.615
What's the difference between an introvert mathematician and an extrovert mathematician? An introvert mathematician looks at his shoes when he's talking to you. An extrovert mathematician looks at YOUR shoes.
A physicist joke...
A physicist goes into an ice cream parlor every week. He always orders an ice cream sundae and offers one to the empty stool next to him. One day the owner of the shop asks the physicist, "Why do you do that?" The physicist replies, "Well, quantum mechanics teaches us that there is a chance that the matter above this stool will spontaneously transform into a beautiful woman who will accept my offer of an ice cream and fall in love with me." The owner says, "We have beautiful women come in here all the time. Why don't you offer one of them an ice cream and maybe she'll fall in love with you." And the physicist replies, "Yeah, right! What are the odds of THAT happening?"
(I heard this joke on"The Big Bang Theory". They got it from Nobel winning physicist George Smoot. Penny apparently tells it a lot better.)
Update: I recently learned that the actual author of this joke is Kevin L. Schwartz.