14
$\begingroup$

Hi I have just found the proof that 90 equals 95 and was wondering if I have made some mistake. If so, which step in my proof is not true?

Definitions:
1. $\angle ABC=90^{\circ}$
2. $\angle BCD=95^{\circ}$
3. $|AB|=|CD|$
4. $M:=$ the center of $BC$
5. $N:=$ the center of $AD$
6. $l:=$ a line perpendicular to $BC$ passing through $M$
7. $m:=$ a line perpendicular to $AD$ passing through $N$
8. $S:=$ is the cross-section of $l$ and $m$

Based on definitions 1 through 8 we can draw the following image: 90 = 95

Based on the definitions we can derive the following:
9. $\triangle BSC$ is isosceles (follows from 4, 6 and 8)
10. $\triangle ASD$ is isosceles (follows from 5, 7 and 8)
11. $|BS|=|CS|$ (follows from 9)
12. $|AS|=|DS|$ (follows from 10)
13. $\triangle ABS\cong\triangle DCS$ (follows from 3, 11 and 12)
14. $\angle ABS=\angle DCS$ (follows from 13)
15. $\angle CBS=\angle BCS$ (follows from 9)
16. $\angle ABC=\angle ABS - \angle CBS=\angle DCS-\angle BCS=\angle BCD$ (follows from 14 and 15)
17. $90^{\circ}=95^{\circ}$ (follows from 1, 2 and 16)

Note: point $S$ is indeed lying above $BC$. If however it would be below $BC$, then the 'minus' in step 16 would simply have to be changed into a 'plus'.

Also note: The image is not drawn to scale. It only serves as to provide the reader with a intuitive view of the proof.

Also also note: before posting, I have first investigated if this type of question would be appropriate. Based on How come 32.5 = 31.5? and the following meta Questions about math jokes I have decided to post this question.

  • 1
    This one and its variants are actually fairly well-known: see http://en.wikipedia.org/wiki/Mathematical_fallacy#Geometry for a spoiler. But finding the error is still a fun puzzle.2010-10-22
  • 8
    Hav you tried drawing an *accurate* diagram?2010-10-22
  • 0
    @freestorageaccount Wow, I got this one through one of my uncles, but was not able to find anything about it on the internet. I knew there had to be something, but I just did not know the right terms to search for it. I shall forward that link to my uncle ^^.2010-10-22
  • 0
    @Robin what is not accurate about it?2010-10-22
  • 0
    Shhh, Robin -- don't ruin the fun part.2010-10-22
  • 1
    @Robin, no doubt that would help the intuition, but surely the wrongness of the proof has to be independent of the diagram.2010-10-22
  • 3
    @Matthijs: "through one of my uncles" - was it by chance Uncle Shelby?? (http://en.wikipedia.org/wiki/Uncle_Shelby%27s_ABZ_Book) "Or is it correct?" Uhm... yes... 90 = 95, from which we can conclude that pigs fly.2010-10-22
  • 1
    This was actually quite fun to draw and notice the error :)2010-10-22
  • 0
    As a hint, the diagram provided isn't actually representative of the given constraints.2010-10-22
  • 0
    About half a year ago I posted this on MathOverflow, but it wasn't received as well as I had expected :D. http://mathoverflow.net/questions/22609/impossible-triangle-proving-that-90-95-closed . Also, my formulation of the question is a bit better here than I did it there. I have also drawn this one on the white board next to the coffee machine at work. Every time I walked by the coffee machine, there would be one or two people standing in front of the white board, coffee in hand, saying things like:"This is not correct!".2010-10-22
  • 4
    Or is it correct?2010-12-01

2 Answers 2

14

Your statement 16 depends on the way in which the diagram is drawn to know that ∠DCS = ∠DCB + ∠BCS.

  • 0
    How is it false then? PS: use dollar signs to encapsulate math. You wanted to type: \angle DCS=\angle DCB+\angle BCS2010-10-22
  • 3
    @Matthis: Carry out the construction in the proof yourself using a geometry set (you can get by with a ruled sheet and a ruler) and you will immediately see what is wrong with the diagram.2010-10-22
  • 0
    @Matt: I believe Isaac knows about the latex. The ∠ is an html escape code. Unfortunately, I don't think that exists, though.2010-10-22
  • 0
    @Matt, @Matthijs: That's odd—`∠` renders correctly in Chrome... [Apparently, I was supposed to use `∠`, but even that doesn't work in IE6 and IE7](http://stackoverflow.com/questions/709827/displaying-angle-symbol-in-html).2010-10-22
  • 4
    @Matthijs: Specifically, 16 depends on the (false) assertion from the diagram that DS is "between" DA and DC, when it is in fact on the "other side" of DC.2010-10-22
44

$$ \begin{array}{l} 0\in\mathbb N\\ \forall n\in \mathbb N : n'\in \mathbb N\\ \hline 0'\in\mathbb N\\ \forall n\in \mathbb N : n'\in \mathbb N\\ \hline 0''\in\mathbb N\\ \forall n\in \mathbb N : n'\in \mathbb N\\ \hline 0'''\in\mathbb N\\ \forall n\in \mathbb N : n'\in \mathbb N\\ \hline 0''''\in\mathbb N\\ \forall n\in \mathbb N : n'\neq0\\ \hline 0'''''\neq0\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''\neq0'\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''\neq0''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''\neq0'''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''\neq0''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''\neq0'''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''\neq0''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''\neq0'''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''\neq0''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''\neq0'''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''\neq0''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''\neq0'''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''\neq0''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''\neq0'''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''\neq0''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''\neq0'''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''\neq0''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''\neq0'''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''\neq0''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''\neq0'''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''\neq0''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''\neq0'''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''\neq0''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline \phantom{0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''} \end{array} $$ $$ \begin{array}{l} 0'''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 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n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline \phantom{0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''} \end{array} $$ $$ \begin{array}{l} 0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline \phantom{0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''} \end{array} $$ $$ \begin{array}{l} 0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \forall m,n\in \mathbb N:m\neq n\rightarrow m'\neq n' \\ \hline 0'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\neq0''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''\\ \\ \square \end{array} $$

  • 3
    This doesn't seem to have anything to do with the original question—am I missing something?2011-07-09
  • 1
    LOL - a good one!2011-07-09
  • 5
    Apparently, using your argument and matthijs proof, it follows that arithmetic is inconsistent ;-)2011-07-09
  • 12
    @Isaac: I think you are. This is a proof from the Peano axioms that $95\neq90$.2011-07-09
  • 6
    @jorki: Sure, but that doesn't address the original question of what the mistake is in the geometric proof, nor does it provide any insight related to the original question.2011-07-09
  • 3
    @Isaac: I took the last paragraph of the question, together with Matthijs' last comment under the question, to imply that the question was intended as a joke, so I replied with a joke. Also, note that the question in the title has two parts; I was responding to the second part, to which my answer is quite relevant ;-)2011-07-09
  • 0
    Very clever. ${}{}{}$2011-07-09
  • 0
    @joriki: Well done. (And your answer does address the first sentence of the post.)2011-07-09
  • 27
    lol, btw. I think there is a mistake in line $0′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′′$ ;)2011-07-09
  • 0
    @joriki: I read your answer yesterday and it still amuses me. I like your sense of humour : )2011-12-03
  • 3
    -1. This doesn't really answer the question.2012-12-27
  • 10
    @Marvis: It's clearly not intended to answer the question. Do you feel that this sort of humour is out of place on this site?2012-12-28
  • 10
    @joriki A short good humored comment is fine with me. But I feel this answer will only add to the OP's confusion, since the OP might not even understand what you are trying to convey and the motivation behind your answer. This is, of course, just my opinion. Given that your answer has received $15$ up-votes compared to just $3$ down-votes, clearly the rest of the site believe such an answer is fine.2012-12-28
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    @Marvis: Note that I answered almost a year after the question had been properly answered and the proper answer had been accepted; the potential for confusing the OP at this point was probably low.2013-03-11
  • 0
    It could have been shorter using induction :). I agree with @claudi85 though: together with my proof, you have proven by contradiction that the Peano axioms are false.2013-03-11
  • 0
    a prime is missing in 97th line! right?!2013-05-07
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    And also in line 143!2013-05-07
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    @Cutie: I'm not sure how you're counting the lines. The way I'm counting the lines, the $97$-th line says $48\ne43$, an it seems to have the right number of primes. Could you please point out the problem more specifically?2013-05-07
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    If you scroll through the post really fast, it looks like an animation.2014-07-08
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    This is the longest answer on the site.2016-06-11