Here are som Math jokes I have (some are lame and you may not get some others):
e^x is walking down the road one day when he meets several other functions coming the other way. One of them, x^2, cries "Run for your life! A differential is coming! He's already eliminated some constants!" as he runs past. "Hah!" exclaimed e^x, "I'm not afraid of any differential; I'm e^x, and he can't affect me." So he walked on a little further, and, sure enough, spied a differential coming towards him. He approached boldly and declared, "Hi, I'm e^x"
"Hello," replied the differential, grinning broadly, "I'm d/dy"
A physicist, a biologist, and a mathematician are looking at a house. 2 people go in and 3 come out. The physicist says "Our initial measurement must have been inaccurate." The biologist says ,"They must have reproduced." The mathematician says, "If one more person enters, the house will be empty."
There were three medieval kingdoms on the shores of a lake. There was an island in the middle of the lake, over which the kingdoms had been fighting for years. Finally, the three kings decided that they would send their knights out to do battle, and the winner would take the island.
The night before the battle, the knights and their squires pitched camp and readied themselves for the fight. The first kingdom had 12 knights, and each knight had five squires, all of whom were busily polishing armor, brushing horses, and cooking food. The second kingdom had twenty knights, and each knight had 10 squires. Everyone at that camp was also busy preparing for battle. At the camp of the third kingdom, there was only one knight, with his squire. This squire took a large pot and hung it from a looped rope in a tall tree. He busied himself preparing the meal, while the knight polished his own armor.
When the hour of the battle came, the three kingdoms sent their squires out to fight (this was too trivial a matter for the knights to join in).
The battle raged, and when the dust had cleared, the only person left was the lone squire from the third kingdom, having defeated the squires from the other two kingdoms, thus proving that the squire of the high pot and noose is equal to the sum of the squires of the other two sides.
during the night, an engineer's house catches fire. he wakes up, picks up the extinguisher, sprays wildly everywhere until the fire is put out, and goes back to bed.
the next night, the physicist's house next door catches fire. he wakes up, does a few brief calculations, douses the fire with one brilliantly aimed shot with an extinguisher, and goes back to bed.
the next night, the mathematician's house across the street catches fire. he wakes up, walks over to the physicist and engineer's houses, drags them over to his burning house and onto his burning bed, and leaves, thereby reducing it to a previously solved problem (and conveniently forgets the fire extinguisher in the process)
A bunch of mathematicians and engineers are taking the train to a congress. The mathematicians hold their ticket nervously their hand all the time, while the engineers haven't even bought a ticket,except one. The mathematicians are whining incessantly about it, the engineers just keep chatting.
When the train conductor comes, all the math guys immediately show their tickets, while the engineers quickly jump into a restroom, in an organised way. The conductor asks for the card, that one card is shoved under the door--->problem solved.
When the congress is over and they return, the mathematicians think they can do it just as well, and one of them holds a ticket, and all the other ones sit really closely to him, nervously/giggling...until they see the engineers don't have any ticket at all this time! Again they start whining...until the train conductor comes!
They all jump into one restroom, so do the engineers...except one, who quickly goes by the other restroom and ask :"Ticket please", before joining the others..
How to prove any odd number larger than 1 is prime...
Mathematician:
3 is prime, 5 is prime, 7 is prime, and by induction we have that all the odd integers are prime.
Physicist:
3 is prime, 5 is prime, 7 is prime, 9 is an experimental error...
Engineer:
3 is prime, 5 is prime, 7 is prime, 9 is prime...
Chemist:
3 is prime, 5 is prime... hey, let's publish!
Modern physicist using renormalization:
3 is prime, 5 is prime, 7 is prime, 9 is ... 9/3 is prime, 11 is prime, 13 is prime, 15 is ... 15/3 is prime, 17 is prime, 19 is prime, 21 is ... 21/3 is prime...
Quantum Physicist:
All numbers are equally prime and non-prime until observed.
Professor:
3 is prime, 5 is prime, 7 is prime, and the rest are left as an exercise for the student.
Confused Undergraduate:
Let p be any prime number larger than 2. Then p is not divisible by 2, so p is odd. QED
Measure nontheorist:
There are exactly as many odd numbers as primes (Euclid, Cantor), and exactly one even prime (namely 2), so there must be exactly one odd nonprime (namely 1).
Computer Scientist:
10 is prime, 11 is prime, 101 is prime...
Programmer:
3 is prime, 5 is prime, 7 is prime, 9 will be fixed in the next release, ...
C programmer:
03 is prime, 05 is prime, 07 is prime, 09 is really 011 which everyone knows is prime, ...
Windows programmer:
3 is prime. Wait...
Mac programmer:
3 is prime, 5 is prime, 7 is prime, 7 is prime, 7 is prime, 7 is prime
ZX-81 Computer Programmer:
3 is prime, Out of Memory.
Pentium owner:
3 is prime, 5 is prime, 7 is prime, 8.9999978 is prime...
Logician:
Hypothesis: All odd numbers are prime
Proof:
If a proof exists, then the hypothesis must be true
The proof exists; you're reading it now.
From 1 and 2 follows that all odd numbers are prime
Here are some nice "proofs" I thought everyone might enjoy.
Theorems
Here, the powerful mathematical methods are successively applied to the "real life problems".
Interesting Theorem:
All positive integers are interesting.
Proof:
Assume the contrary. Then there is a lowest non-interesting positive integer. But, hey, that's pretty interesting! A contradiction.
Boring Theorem:
All positive integers are boring.
Proof:
Assume the contrary. Then there is a lowest non-boring positive integer. Who cares!
Discovery.
Mathematicians have announced the existence of a new whole number which lies between 27 and 28. "We don't know why it's there or what it does," says Cambridge mathematician, Dr. Hilliard Haliard, "we only know that it doesn't behave properly when put into equations, and that it is divisible by six, though only once."
Theorem:
There are two groups of people in the world; those who believe that the world can be divided into two groups of people, and those who don't.
Theorem:
The world is divided into two classes:
people who say "The world is divided into two classes",
and people who say: The world is divided into two classes:
people who say: "The world is divided into two classes",
and people who say: The world is divided into two classes:
people who say ...
There are three kinds of people in the world; those who can count and those who can't.
There are 10 kinds of people in the world, those who understand binary math, and those who don't.
There really are only two types of people in the world, those that DON'T
DO MATH, and those that take care of them.
"The world is everywhere dense with idiots."
Cat Theorem:
A cat has nine tails.
Proof:
No cat has eight tails. A cat has one tail more than no cat. Therefore, a cat has nine tails.
Salary Theorem
The less you know, the more you make.
Proof:
Postulate 1: Knowledge is Power.
Postulate 2: Time is Money.
As every engineer knows: Power = Work / Time
And since Knowledge = Power and Time = Money
It is therefore true that Knowledge = Work / Money .
Solving for Money, we get:
Money = Work / Knowledge
Thus, as Knowledge approaches zero, Money approaches infinity, regardless of the amount of Work done.
Q: How do you tell that you are in the hands of the Mathematical Mafia?
A: They make you an offer that you can't understand.
The cherry theorem (a puzzle that reminds some of calculus theorems)
Q: What is a small, red, round thing that has a cherry pit inside?
A: A cherry.
Notes on the horse colors problem
Lemma 1. All horses are the same color. (Proof by induction)
Proof It is obvious that one horse is the same color. Let us assume the proposition P(k) that k horses are the same color and use this to imply that k+1 horses are the same color. Given the set of k+1 horses, we remove one horse; then the remaining k horses are the same color, by hypothesis. We remove another horse and replace the first; the k horses, by hypothesis, are again the same color. We repeat this until by exhaustion the k+1 sets of k horses have been shown to be the same color. It follows that since every horse is the same color as every other horse, P(k) entails P(k+1). But since we have shown P(1) to be true, P is true for all succeeding values of k, that is, all horses are the same color.
Theorem 1. Every horse has an infinite number of legs. (Proof by intimidation.)
Proof Horses have an even number of legs. Behind they have two legs and in front they have fore legs. This makes six legs, which is certainly an odd number of legs for a horse. But the only number that is both odd and even is infinity. Therefore horses have an infinite number of legs. Now to show that this is general, suppose that somewhere there is a horse with a finite number of legs. But that is a horse of another color, and by the lemma that does not exist.
Corollary 1 Everything is the same color.
Proof The proof of lemma 1 does not depend at all on the nature of the object under consideration. The predicate of the antecedent of the universally-quantified conditional 'For all x, if x is a horse, then x is the same color,' namely 'is a horse' may be generalized to 'is anything' without affecting the validity of the proof; hence, 'for all x, if x is anything, x is the same color.'
Corollary 2 Everything is white.
Proof If a sentential formula in x is logically true, then any particular substitution instance of it is a true sentence. In particular then: 'for all x, if x is an elephant, then x is the same color' is true. Now it is manifestly axiomatic that white elephants exist (for proof by blatant assertion consult Mark Twain 'The Stolen White Elephant'). Therefore all elephants are white. By corollary 1 everything is white.
Theorem 2 Alexander the Great did not exist and he had an infinite number of limbs.
Proof We prove this theorem in two parts. First we note the obvious fact that historians always tell the truth (for historians always take a stand, and therefore they cannot lie). Hence we have the historically true sentence, 'If Alexander the Great existed, then he rode a black horse Bucephalus.' But we know by corollary 2 everything is white; hence Alexander could not have ridden a black horse. Since the consequent of the conditional is false, in order for the whole statement to be true the antecedent must be false. Hence Alexander the Great did not exist.
We have also the historically true statement that Alexander was warned by an oracle that he would meet death if he crossed a certain river. He had two legs; and 'forewarned is four-armed.' This gives him six limbs, an even number, which is certainly an odd number of limbs for a man. Now the only number which is even and odd is infinity; hence Alexander had an infinite number of limbs. We have thus proved that Alexander the Great did not exist and that he had an infinite number of limbs.
According to statistics, there are 42 million alligator eggs laid every year. Of those, only about half get hatched. Of those that hatch, three fourths of them get eaten by predators in the first 36 days. And of the rest, only 5 percent get to be a year old for one reason or another. Isn't statistics wonderful? If it weren't for statistics, we'd be eaten by alligators!
Hopefully some of these will be better than some of the previously posted jokes 
Anyway you feel like (personal messages, spam, poke me with a stick, even better if it's Weregoose's stick of optimization, etc.) 
