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Math One-Liners

Math problems? Call 1-800-[(10x)(13i)^2]-[sin(xy)/2.362x]. If parallel lines meet at infinity - infinity must be a very noisy place with all those lines crashing together!

- Maths Teacher: Now suppose the number of sheep is x...

- Student: Yes sir, but what happens if the number of sheep is not x?

Zenophobia: the irrational fear of convergent sequences.

Philosophy is a game with objectives and no rules. Mathematics is a game with rules and no objectives.

If I had only one day left to live, I would live it in my statistics class: it would seem so much longer.

Infinite Hotels

A very large mathematical convention was held in Las Vegas. The conventioneers filled two hotels, each with an infinite number of rooms. The hotels were across the street from each other and were owned by brothers. One evening, while everyone was out at a bar-b-que, one of the hotels burned to the ground. The brothers got together and worked out a plan. In the remaining hotel, they moved all guests to twice their room number -- room 101 moved to 202, room 1234 moved to room 2468, etc. Then all the odd number rooms were empty, and there were an infinite number of odd rooms. So the guests from the other hotel moved into them

Fencing In Sheep

An engineer, a physicist, and a mathematician are trying to set up a fenced-in area for some sheep, but they have a limited amount of building material. The engineer gets up first and makes a square fence with the material, reasoning that it's a pretty good working solution.

- No no - says the physicist - there's a better way.

He takes the fence and makes a circular pen, showing how it encompasses the maximum possible space with the given material.

Then the mathematician speaks up:

- No, no, there's an even better way.

To the others' amusement he proceeds to construct a little tiny fence around himself, then declares:

- I define myself to be on the outside.

Elephant in the Refrigerator

Analysis:

  1. Differentiate it and put into the refrig. Then integrate it in the refrig.
  2. Redefine the measure on the referigerator (or the elephant).
  3. Apply the Banach-Tarsky theorem.

Number theory:

  1. First factorize, second multiply.
  2. Use induction. You can always squeeze a bit more in.

Algebra:

  1. Step 1. Show that the parts of it can be put into the refrig. Step 2. Show that the refrig. is closed under the addition.
  2. Take the appropriate universal refrigerator and get a surjection from refrigerator to elephant.
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Geometry Drugs

- Psst, c'mere - said the shifty-eyed man wearing a long black trenchcoat, as he beckoned me off the rainy street into a damp dark alley. I followed.

- What are you selling?

- Geometrical algebra drugs.

- Huh!?

- Geometry drugs. Ya got your uppers, your downers, your sidewaysers, your inside-outers...

- Stop right there - I interrupted.

- I've never heard of inside-outers.

- Oh, man, you'll love 'em. Makes you feel like M.C. ever-lovin' Escher on a particularly weird day.

- Go on...

- OK, your inside-outers, your arbitrary bilinear mappers, and here, heh, here are the best ones - he said, pulling out a large clear bottle of orange pills.

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The Long Green Crocodile

Prove that the crocodile is longer than it is wide.

Lemma 1. The crocodile is longer than it is green: Let's look at the crocodile. It is long on the top and on the bottom, but it is green only on the top. Therefore, the crocodile is longer than it is green.

Lemma 2. The crocodile is greener than it is wide: Let's look at the crocodile. It is green along its length and width, but it is wide only along its width. Therefore, the crocodile is greener than it is wide.

From Lemma 1 and Lemma 2 we conclude that the crocodile is longer than it is wide.

One Equals One Half

Theorem: 1 = 1/2

Proof:
We can re-write the infinite series 1/(1*3) + 1/(3*5) + 1/(5*7) + 1/(7*9)+... as 1/2((1/1 - 1/3) + (1/3 - 1/5) + (1/5 - 1/7) + (1/7 - 1/9) + ... ).

All terms after 1/1 cancel, so that the sum is 1/2.

We can also re-write the series as (1/1 - 2/3) + (2/3 - 3/5) + (3/5 - 4/7)+ (4/7 - 5/9) + ...

All terms after 1/1 cancel, so that the sum is 1.

Thus 1/2 = 1.

Log of Negative One

Theorem: log(-1) = 0

Proof:
a. log[(-1)^2] = 2 * log(-1)
On the other hand:
b. log[(-1)^2] = log(1) = 0
Combining a) and b) gives:
2* log(-1) = 0
Divide both sides by 2:
log(-1) = 0

One Equals Negative One

Theorem: 1 = -1

Proof:
1 = sqrt(1) = sqrt(-1 * -1) = sqrt(-1) * sqrt(-1) = 1^ = -1

Also one can disprove the axiom that things equal to the same thing are equal to each other.
1 = sqrt(1)
and -1 = sqrt(1)
Therefore 1 = -1

As an alternative method for solving:

Theorem: 1 = -1

Proof:

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All Numbers Are Equal

Theorem: All numbers are equal.

Proof: Choose arbitrary a and b, and let t = a + b. Then
a + b = t
(a + b)(a - b) = t(a - b)
a^2 - b^2 = ta - tb
a^2 - ta = b^2 - tb
a^2 - ta + (t^2)/4 = b^2 - tb + (t^2)/4
(a - t/2)^2 = (b - t/2)^2
a - t/2 = b - t/2
a = b

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N Equals N Plus One

Theorem: n=n+1
Proof:
(n+1)^2 = n^2 + 2*n + 1
Bring 2n+1 to the left:
(n+1)^2 - (2n+1) = n^2
Substract n(2n+1) from both sides and factoring, we have:
(n+1)^2 - (n+1)(2n+1) = n^2 - n(2n+1)
Adding 1/4(2n+1)^2 to both sides yields:
(n+1)^2 - (n+1)(2n+1) + 1/4(2n+1)^2 = n^2 - n(2n+1) + 1/4(2n+1)^2
This may be written:

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Dollar Equals Ten Cents

Theorem: 1$ = 10 cent
Proof:
We know that $1 = 100 cents
Divide both sides by 100
$ 1/100 = 100/100 cents
=> $ 1/100 = 1 cent
Take square root both side
=> squr($1/100) = squr (1 cent)
=> $ 1/10 = 1 cent
Multiply both side by 10

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Dollars Equal Cents

Theorem: 1$ = 1c.

Proof:
And another that gives you a sense of money disappearing.
1$ = 100c
= (10c)^2
= (0.1$)^2
= 0.01$
= 1c
Here $ means dollars and c means cents. This one is scary in that I have seen PhD's in math who were unable to see what was wrong with this one. Actually I am crossposting this to sci.physics because I think that the latter makes a very nice introduction to the importance of keeping track of your dimensions.

Numbers Equal Zero

Theorem : All numbers are equal to zero.

Proof: Suppose that a=b. Then
a = b
a^2 = ab
a^2 - b^2 = ab - b^2
(a + b)(a - b) = b(a - b)
a + b = b
a = 0
Furthermore if a + b = b, and a = b, then b + b = b, and 2b = b, which mean that 2 = 1.

Equal Positive Integers

Theorem: All positive integers are equal.

Proof: Sufficient to show that for any two positive integers, A and B, A = B.
Further, it is sufficient to show that for all N > 0, if A and B (positive integers) satisfy (MAX(A, B) = N) then A = B.
Proceed by induction.

If N = 1, then A and B, being positive integers, must both be 1. So A = B.
Assume that the theorem is true for some value k. Take A and B with MAX(A, B) = k+1. Then MAX((A-1), (B-1)) = k. And hence (A-1) = (B-1). Consequently, A = B.