Clarification about a given axiom system.












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I am now currently studying Combinatorics of Finite Geometries. One problem asks if the given axiom system below is consistent or inconsistent.




  1. There are five points and six lines.

  2. Each point is in at most two lines.

  3. Each line contains two points.


Is the given axiom system consistent with a sample structure given below? enter image description here



My answer is no since axiom 2 will be violated. In particular there are points that are contained in six lines.



My questions are: (1) Am I correct? (2) If I am correct is there a possible structure that satisfies the given axiom system?



Thanks for the help.










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    0












    $begingroup$


    I am now currently studying Combinatorics of Finite Geometries. One problem asks if the given axiom system below is consistent or inconsistent.




    1. There are five points and six lines.

    2. Each point is in at most two lines.

    3. Each line contains two points.


    Is the given axiom system consistent with a sample structure given below? enter image description here



    My answer is no since axiom 2 will be violated. In particular there are points that are contained in six lines.



    My questions are: (1) Am I correct? (2) If I am correct is there a possible structure that satisfies the given axiom system?



    Thanks for the help.










    share|cite|improve this question











    $endgroup$















      0












      0








      0





      $begingroup$


      I am now currently studying Combinatorics of Finite Geometries. One problem asks if the given axiom system below is consistent or inconsistent.




      1. There are five points and six lines.

      2. Each point is in at most two lines.

      3. Each line contains two points.


      Is the given axiom system consistent with a sample structure given below? enter image description here



      My answer is no since axiom 2 will be violated. In particular there are points that are contained in six lines.



      My questions are: (1) Am I correct? (2) If I am correct is there a possible structure that satisfies the given axiom system?



      Thanks for the help.










      share|cite|improve this question











      $endgroup$




      I am now currently studying Combinatorics of Finite Geometries. One problem asks if the given axiom system below is consistent or inconsistent.




      1. There are five points and six lines.

      2. Each point is in at most two lines.

      3. Each line contains two points.


      Is the given axiom system consistent with a sample structure given below? enter image description here



      My answer is no since axiom 2 will be violated. In particular there are points that are contained in six lines.



      My questions are: (1) Am I correct? (2) If I am correct is there a possible structure that satisfies the given axiom system?



      Thanks for the help.







      geometry combinatorial-geometry






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      edited Jan 12 at 4:59







      Jr Antalan

















      asked Jan 9 at 10:52









      Jr AntalanJr Antalan

      1,2881822




      1,2881822






















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          $begingroup$

          (1) You are correct. I hope your teacher isn't the one who thought the system in the picture satisfies the axioms.



          (2) No, the given axiom system is not satisfiable. How many pairs $(p,L)$ are there, consisting of a point $p$ which is on a line $L$? By axioms 1 and 2, there are at most $10$ such pairs; but by axioms 1 and 3, there must be $12$ of them. The axioms are inconsistent.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thanks @bof. All clear to me now.
            $endgroup$
            – Jr Antalan
            Jan 9 at 11:40











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          $begingroup$

          (1) You are correct. I hope your teacher isn't the one who thought the system in the picture satisfies the axioms.



          (2) No, the given axiom system is not satisfiable. How many pairs $(p,L)$ are there, consisting of a point $p$ which is on a line $L$? By axioms 1 and 2, there are at most $10$ such pairs; but by axioms 1 and 3, there must be $12$ of them. The axioms are inconsistent.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thanks @bof. All clear to me now.
            $endgroup$
            – Jr Antalan
            Jan 9 at 11:40
















          1












          $begingroup$

          (1) You are correct. I hope your teacher isn't the one who thought the system in the picture satisfies the axioms.



          (2) No, the given axiom system is not satisfiable. How many pairs $(p,L)$ are there, consisting of a point $p$ which is on a line $L$? By axioms 1 and 2, there are at most $10$ such pairs; but by axioms 1 and 3, there must be $12$ of them. The axioms are inconsistent.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Thanks @bof. All clear to me now.
            $endgroup$
            – Jr Antalan
            Jan 9 at 11:40














          1












          1








          1





          $begingroup$

          (1) You are correct. I hope your teacher isn't the one who thought the system in the picture satisfies the axioms.



          (2) No, the given axiom system is not satisfiable. How many pairs $(p,L)$ are there, consisting of a point $p$ which is on a line $L$? By axioms 1 and 2, there are at most $10$ such pairs; but by axioms 1 and 3, there must be $12$ of them. The axioms are inconsistent.






          share|cite|improve this answer









          $endgroup$



          (1) You are correct. I hope your teacher isn't the one who thought the system in the picture satisfies the axioms.



          (2) No, the given axiom system is not satisfiable. How many pairs $(p,L)$ are there, consisting of a point $p$ which is on a line $L$? By axioms 1 and 2, there are at most $10$ such pairs; but by axioms 1 and 3, there must be $12$ of them. The axioms are inconsistent.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Jan 9 at 11:04









          bofbof

          51.4k557120




          51.4k557120












          • $begingroup$
            Thanks @bof. All clear to me now.
            $endgroup$
            – Jr Antalan
            Jan 9 at 11:40


















          • $begingroup$
            Thanks @bof. All clear to me now.
            $endgroup$
            – Jr Antalan
            Jan 9 at 11:40
















          $begingroup$
          Thanks @bof. All clear to me now.
          $endgroup$
          – Jr Antalan
          Jan 9 at 11:40




          $begingroup$
          Thanks @bof. All clear to me now.
          $endgroup$
          – Jr Antalan
          Jan 9 at 11:40


















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