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Guest Comic - December 19, 2009
Rating: 4.6/5 (65 votes cast)
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A big thanks to Joe for creating today's comic.


Spiked Math Comic - Guest Comic

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the error's at line 5. 2(pi)x =/= 9

Dangerous things, those square roots. Especially when one forgets there are two branches!

That's not the error. In the second panel, he accidentally switched lines 5 and 6 but they do still hold. The issue is at the end.

3 - x = (6 - π - 3)/2 = (-π+3)/2
π - x = (2π - π - 3)/2 = (π - 3)/2 = - (3 - x)

So (3 - x)^2 = (π - x)^2, but 3 - x ≠ π - x

Either way, AWESOME. I'm using this with my not so math-literate friends.

Actually, it appears to be correct up to and including line 7.
(3-x)^2 = (pi-x)^2 for x approximately 3.0707963

The mistake is forgetting that there are *two* square roots for evey number, and the equation need only hold for one of the possiblities. In this case, the wrong one is used, and the euqation is false.

What Sameer Farooq said.

On the other hand, once you prove a contradiction, like 3 ≠ π and 3 = π, you can prove anything!

I guess you used the (alternative) definition of absolute value:
|x| = sqrt(x^2)

However, it is always necessary to consider the case when the expression is negative. So, the standard definition of absolute value comes in handy:
x, if x >= 0
-x, if x < 0

In this example, one doesn't know the value of pi-x (or, for that matter, 3-x), since x is unknown. Its value becomes evident when you discard the impossible case.

...You realise, that in this case, pi is just being used as a pronumeral? It doesn't have to stand for 3.14...

You could set up an equation where pi = 5, too.

Umm, in theory, π could be anything. In practice, it has one use and one use only--the ratio of a circle's circumference to it's diameter. Try to use it for anything else, and you will mess a lot of people up.

You might be surprised to see how often pi turns up in branches like probability and analysis, recall Eulers identity?

...in Euler's identity, pi still denotes the circle ratio. But I would disagree in Bmonk that in practice, pi crops up in other areas, for example, the prime counting function.

Nothing is wrong with the math except using the wrong square root
Using my calculator...x=(pi + 3)/2 ~ 3.07
then...3-x = -.07
and....pi-x ~ .07

Thus the wrong square root was used...i.e. a=+/-b
+ b was used instead of - b

-b = x-pi...all this means is 3-x = x-pi...or pi ~ 2x - 3 = 3.14

Just wanted to point out that this works for any two numbers: translating to their mean, they look like +/- something, vulnerable to the wrong square root jedi mind trick.

I just can't get why your last image is exactly the same than http://nsa09.casimages.com/img/2009/09/27/090927113734328167.jpg , which comes from a totally different topic on a french popular forum at http://www.gamekult.com/forum/lire_n550218_page1/.
Sorry for the NreallySFW.

FUUU!!!! is a meme, and this one is the "mathematical" version of it, :P

2.718281828459045..., XD

I don't understand why you're getting intimidated by the suymbol of pi.. It could any general constant say A. So, x = (A+3)/2.. so mathematics says that given this you can't find out a value of x indepnedent of A or vice-versa.. The fallacy lies in adding x^2 to both sides in line 6, by which you've added an unnecessary root for solving for x by yourself(which is 3 as we later learn). Now while solving for the quadratic equations, we have to avoid the root we have added ourselves(which comes by taking 3-x = A-x in penultimate line.) The original result comes from 3-x = x-A, which gives us x = (3+A)/2 just as we had started. The other result i.e. x=A=3 was our own stupidity in adding x^2 to both sides.. we can't just do that.

This site is weird.. thrice it told me I couldn't post because I hadn't signed up.. The next refresh I see 3 copies of the comment here, and now it doesn't even give me an option to delete the redundant copies.

Not sure why that happened, you should be able to comment without signing up. It might be a javascript problem though?

Anyway I signed up. Could you please put a button to be able to delete a comment? Also, does it anywhere indicate whether I'm signed in or not. I'd just say this is a great site(pure fun), keep it going :) !

Assuming pi is the value of pi, the answer to this equation is insanely easy and straight forward. Rounding to a few decimal points for simplicity of the answer, if solving for X, X=3.070795

Now, I am definitely not a great mathemagician, but as far as I can see the problem in the equation is that both sides are multiplied by zero in the third line.
Tell me, if I'm off.

@Bertram y do u assume pi=3??? and more over wats wrong in multiplyin both side by zero??? u cant divide but def can multiply....

I CAN divide by 0! (ignore factorial): 1/0=∞.

Not really getting what you're all blabbering about, the flaw is easy to find:
pi = 3 means that x would be 3 (see first line)
But in the second to last line you divided by x-3, which is zero, you can't divide by zero.
It's the same problem as this:
a = 1 and b = 1:
a = b
-a = -b
-ab = -(b^2)
a^2 - ab = a^2 - b^2
a(a-b) = (a+b)(a-b)
a = a + b
1 = 2

This only adds up because I divided by zero

@Paul: He hasn't divided by (x-3) or (π-3). He has simply taken the wrong sign for the square root. :) But i do like ur 1=2 example. :)

i dont get it

Another, similar proof:
And therefore 2=0, 1=0, and for all x and y, 1(x-y)=0(x-y) & x-y=0. Thus, x=y FOR ALL VALUES OF X AND Y.

Bertram is right. Since pi was not defined and in this case is just an arbitrary constant, multiplying both sides by (Π - 3) adds in a solution where (Π - 3) = 0 and therefore Π = 3.

But pi is ratio of circumference/diameter, AND I KNOW IT TO 88 DIGITS!
...which means I'm in the top 48,96%.


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Hello my fellow math geeks. My name is Mike and I am the creator of Spiked Math Comics, a math comic dedicated to humor, educate and entertain the geek in you. Beware though, there might be some math involved :D

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