Proof the Dot Conjecture

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I was reading the book Fermat's Last Theorem Simon Singh and in chapter 3 he mentions the "Dot Conjecture", and gives a proof in the appendix.



However, the "proof" seems to me as a just more elaborate way of stating that the proof is obvious and trivial. I was talking with a friend and she is also clueless. Furthermore, I couldn't even find any reference to it by googling.
I realise that, since this is a pop-math book, he might not be using the "official" name of this conjecture.



If somebody could explain it to me or at least give some link or further reading, I'd be very grateful.



first mention of the dot conjecture



the "proof"







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  • Look up this wiki article. It's a well known theorem, but the proof that you've given is actually quite recent. There were some harder proofs before that one popped up (by Kelly). I wouldn't say that it is in any way trivial. What makes you think that ?
    – Kolja
    Aug 8 at 20:12






  • 1




    Neither of these links works for me. What is the "dot conjecture?"
    – saulspatz
    Aug 8 at 20:47










  • @saulspatz it is impossible to draw a dot diagram such that every line has at least three dots on it, and every dot is connected with every other dot by a line
    – fazan
    Aug 9 at 0:44











  • This is Sylvester's Theorem. Look at this : ics.uci.edu/~eppstein/junkyard/sylvester.html
    – saulspatz
    Aug 9 at 7:43














up vote
0
down vote

favorite












I was reading the book Fermat's Last Theorem Simon Singh and in chapter 3 he mentions the "Dot Conjecture", and gives a proof in the appendix.



However, the "proof" seems to me as a just more elaborate way of stating that the proof is obvious and trivial. I was talking with a friend and she is also clueless. Furthermore, I couldn't even find any reference to it by googling.
I realise that, since this is a pop-math book, he might not be using the "official" name of this conjecture.



If somebody could explain it to me or at least give some link or further reading, I'd be very grateful.



first mention of the dot conjecture



the "proof"







share|cite|improve this question




















  • Look up this wiki article. It's a well known theorem, but the proof that you've given is actually quite recent. There were some harder proofs before that one popped up (by Kelly). I wouldn't say that it is in any way trivial. What makes you think that ?
    – Kolja
    Aug 8 at 20:12






  • 1




    Neither of these links works for me. What is the "dot conjecture?"
    – saulspatz
    Aug 8 at 20:47










  • @saulspatz it is impossible to draw a dot diagram such that every line has at least three dots on it, and every dot is connected with every other dot by a line
    – fazan
    Aug 9 at 0:44











  • This is Sylvester's Theorem. Look at this : ics.uci.edu/~eppstein/junkyard/sylvester.html
    – saulspatz
    Aug 9 at 7:43












up vote
0
down vote

favorite









up vote
0
down vote

favorite











I was reading the book Fermat's Last Theorem Simon Singh and in chapter 3 he mentions the "Dot Conjecture", and gives a proof in the appendix.



However, the "proof" seems to me as a just more elaborate way of stating that the proof is obvious and trivial. I was talking with a friend and she is also clueless. Furthermore, I couldn't even find any reference to it by googling.
I realise that, since this is a pop-math book, he might not be using the "official" name of this conjecture.



If somebody could explain it to me or at least give some link or further reading, I'd be very grateful.



first mention of the dot conjecture



the "proof"







share|cite|improve this question












I was reading the book Fermat's Last Theorem Simon Singh and in chapter 3 he mentions the "Dot Conjecture", and gives a proof in the appendix.



However, the "proof" seems to me as a just more elaborate way of stating that the proof is obvious and trivial. I was talking with a friend and she is also clueless. Furthermore, I couldn't even find any reference to it by googling.
I realise that, since this is a pop-math book, he might not be using the "official" name of this conjecture.



If somebody could explain it to me or at least give some link or further reading, I'd be very grateful.



first mention of the dot conjecture



the "proof"









share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Aug 8 at 20:08









fazan

164




164











  • Look up this wiki article. It's a well known theorem, but the proof that you've given is actually quite recent. There were some harder proofs before that one popped up (by Kelly). I wouldn't say that it is in any way trivial. What makes you think that ?
    – Kolja
    Aug 8 at 20:12






  • 1




    Neither of these links works for me. What is the "dot conjecture?"
    – saulspatz
    Aug 8 at 20:47










  • @saulspatz it is impossible to draw a dot diagram such that every line has at least three dots on it, and every dot is connected with every other dot by a line
    – fazan
    Aug 9 at 0:44











  • This is Sylvester's Theorem. Look at this : ics.uci.edu/~eppstein/junkyard/sylvester.html
    – saulspatz
    Aug 9 at 7:43
















  • Look up this wiki article. It's a well known theorem, but the proof that you've given is actually quite recent. There were some harder proofs before that one popped up (by Kelly). I wouldn't say that it is in any way trivial. What makes you think that ?
    – Kolja
    Aug 8 at 20:12






  • 1




    Neither of these links works for me. What is the "dot conjecture?"
    – saulspatz
    Aug 8 at 20:47










  • @saulspatz it is impossible to draw a dot diagram such that every line has at least three dots on it, and every dot is connected with every other dot by a line
    – fazan
    Aug 9 at 0:44











  • This is Sylvester's Theorem. Look at this : ics.uci.edu/~eppstein/junkyard/sylvester.html
    – saulspatz
    Aug 9 at 7:43















Look up this wiki article. It's a well known theorem, but the proof that you've given is actually quite recent. There were some harder proofs before that one popped up (by Kelly). I wouldn't say that it is in any way trivial. What makes you think that ?
– Kolja
Aug 8 at 20:12




Look up this wiki article. It's a well known theorem, but the proof that you've given is actually quite recent. There were some harder proofs before that one popped up (by Kelly). I wouldn't say that it is in any way trivial. What makes you think that ?
– Kolja
Aug 8 at 20:12




1




1




Neither of these links works for me. What is the "dot conjecture?"
– saulspatz
Aug 8 at 20:47




Neither of these links works for me. What is the "dot conjecture?"
– saulspatz
Aug 8 at 20:47












@saulspatz it is impossible to draw a dot diagram such that every line has at least three dots on it, and every dot is connected with every other dot by a line
– fazan
Aug 9 at 0:44





@saulspatz it is impossible to draw a dot diagram such that every line has at least three dots on it, and every dot is connected with every other dot by a line
– fazan
Aug 9 at 0:44













This is Sylvester's Theorem. Look at this : ics.uci.edu/~eppstein/junkyard/sylvester.html
– saulspatz
Aug 9 at 7:43




This is Sylvester's Theorem. Look at this : ics.uci.edu/~eppstein/junkyard/sylvester.html
– saulspatz
Aug 9 at 7:43










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Taking back the proof from where it stops, imagine that there is a third point on that line (call it $ AB $ where $ A $ is on the left and $ B $ on the right, and call the "closest point" below $ P $), if the third point, say $ C $ is on the left of the picture, then the distance from $ A $ to $ PC $ is shorter than the dashed segment. You get a similar contradiction if $ C $ is on the right, or between $ A $ and $ B $.






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    1 Answer
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    Taking back the proof from where it stops, imagine that there is a third point on that line (call it $ AB $ where $ A $ is on the left and $ B $ on the right, and call the "closest point" below $ P $), if the third point, say $ C $ is on the left of the picture, then the distance from $ A $ to $ PC $ is shorter than the dashed segment. You get a similar contradiction if $ C $ is on the right, or between $ A $ and $ B $.






    share|cite|improve this answer
























      up vote
      0
      down vote













      Taking back the proof from where it stops, imagine that there is a third point on that line (call it $ AB $ where $ A $ is on the left and $ B $ on the right, and call the "closest point" below $ P $), if the third point, say $ C $ is on the left of the picture, then the distance from $ A $ to $ PC $ is shorter than the dashed segment. You get a similar contradiction if $ C $ is on the right, or between $ A $ and $ B $.






      share|cite|improve this answer






















        up vote
        0
        down vote










        up vote
        0
        down vote









        Taking back the proof from where it stops, imagine that there is a third point on that line (call it $ AB $ where $ A $ is on the left and $ B $ on the right, and call the "closest point" below $ P $), if the third point, say $ C $ is on the left of the picture, then the distance from $ A $ to $ PC $ is shorter than the dashed segment. You get a similar contradiction if $ C $ is on the right, or between $ A $ and $ B $.






        share|cite|improve this answer












        Taking back the proof from where it stops, imagine that there is a third point on that line (call it $ AB $ where $ A $ is on the left and $ B $ on the right, and call the "closest point" below $ P $), if the third point, say $ C $ is on the left of the picture, then the distance from $ A $ to $ PC $ is shorter than the dashed segment. You get a similar contradiction if $ C $ is on the right, or between $ A $ and $ B $.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Aug 8 at 20:34









        Arnaud Mortier

        19.2k22159




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