What is the concept of pathological function? [closed]












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mixed derivative theorem:
Mixed partial derivatives Fxy and Fyx are always equal except for pathological functions.



for using mixed derivative theorem function must be non-pathological,so i want a way to find out a function is pathological or not?










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closed as unclear what you're asking by Martin R, Brahadeesh, Shailesh, user10354138, amWhy Dec 7 '18 at 10:37


Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.














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    "pathological" is a somewhat vague name for a function that gives counterexamples to incorrect statements that are not so easy to refute.
    $endgroup$
    – Peter
    Dec 7 '18 at 8:53










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    What do you mean by a pathological function?
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    – Falrach
    Dec 7 '18 at 9:08






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    Some context would be helpful, but its probably what peter wrote
    $endgroup$
    – klirk
    Dec 7 '18 at 9:35










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    If that is all your source text says about when mixed partial derivatives are equal, it's time to throw it away.
    $endgroup$
    – user21820
    Dec 17 '18 at 6:29
















0












$begingroup$


mixed derivative theorem:
Mixed partial derivatives Fxy and Fyx are always equal except for pathological functions.



for using mixed derivative theorem function must be non-pathological,so i want a way to find out a function is pathological or not?










share|cite|improve this question











$endgroup$



closed as unclear what you're asking by Martin R, Brahadeesh, Shailesh, user10354138, amWhy Dec 7 '18 at 10:37


Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.














  • 1




    $begingroup$
    "pathological" is a somewhat vague name for a function that gives counterexamples to incorrect statements that are not so easy to refute.
    $endgroup$
    – Peter
    Dec 7 '18 at 8:53










  • $begingroup$
    What do you mean by a pathological function?
    $endgroup$
    – Falrach
    Dec 7 '18 at 9:08






  • 1




    $begingroup$
    Some context would be helpful, but its probably what peter wrote
    $endgroup$
    – klirk
    Dec 7 '18 at 9:35










  • $begingroup$
    If that is all your source text says about when mixed partial derivatives are equal, it's time to throw it away.
    $endgroup$
    – user21820
    Dec 17 '18 at 6:29














0












0








0





$begingroup$


mixed derivative theorem:
Mixed partial derivatives Fxy and Fyx are always equal except for pathological functions.



for using mixed derivative theorem function must be non-pathological,so i want a way to find out a function is pathological or not?










share|cite|improve this question











$endgroup$




mixed derivative theorem:
Mixed partial derivatives Fxy and Fyx are always equal except for pathological functions.



for using mixed derivative theorem function must be non-pathological,so i want a way to find out a function is pathological or not?







functions derivatives differential






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share|cite|improve this question













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edited Dec 7 '18 at 12:09







alireza khorshidi

















asked Dec 7 '18 at 8:51









alireza khorshidialireza khorshidi

13




13




closed as unclear what you're asking by Martin R, Brahadeesh, Shailesh, user10354138, amWhy Dec 7 '18 at 10:37


Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.









closed as unclear what you're asking by Martin R, Brahadeesh, Shailesh, user10354138, amWhy Dec 7 '18 at 10:37


Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.










  • 1




    $begingroup$
    "pathological" is a somewhat vague name for a function that gives counterexamples to incorrect statements that are not so easy to refute.
    $endgroup$
    – Peter
    Dec 7 '18 at 8:53










  • $begingroup$
    What do you mean by a pathological function?
    $endgroup$
    – Falrach
    Dec 7 '18 at 9:08






  • 1




    $begingroup$
    Some context would be helpful, but its probably what peter wrote
    $endgroup$
    – klirk
    Dec 7 '18 at 9:35










  • $begingroup$
    If that is all your source text says about when mixed partial derivatives are equal, it's time to throw it away.
    $endgroup$
    – user21820
    Dec 17 '18 at 6:29














  • 1




    $begingroup$
    "pathological" is a somewhat vague name for a function that gives counterexamples to incorrect statements that are not so easy to refute.
    $endgroup$
    – Peter
    Dec 7 '18 at 8:53










  • $begingroup$
    What do you mean by a pathological function?
    $endgroup$
    – Falrach
    Dec 7 '18 at 9:08






  • 1




    $begingroup$
    Some context would be helpful, but its probably what peter wrote
    $endgroup$
    – klirk
    Dec 7 '18 at 9:35










  • $begingroup$
    If that is all your source text says about when mixed partial derivatives are equal, it's time to throw it away.
    $endgroup$
    – user21820
    Dec 17 '18 at 6:29








1




1




$begingroup$
"pathological" is a somewhat vague name for a function that gives counterexamples to incorrect statements that are not so easy to refute.
$endgroup$
– Peter
Dec 7 '18 at 8:53




$begingroup$
"pathological" is a somewhat vague name for a function that gives counterexamples to incorrect statements that are not so easy to refute.
$endgroup$
– Peter
Dec 7 '18 at 8:53












$begingroup$
What do you mean by a pathological function?
$endgroup$
– Falrach
Dec 7 '18 at 9:08




$begingroup$
What do you mean by a pathological function?
$endgroup$
– Falrach
Dec 7 '18 at 9:08




1




1




$begingroup$
Some context would be helpful, but its probably what peter wrote
$endgroup$
– klirk
Dec 7 '18 at 9:35




$begingroup$
Some context would be helpful, but its probably what peter wrote
$endgroup$
– klirk
Dec 7 '18 at 9:35












$begingroup$
If that is all your source text says about when mixed partial derivatives are equal, it's time to throw it away.
$endgroup$
– user21820
Dec 17 '18 at 6:29




$begingroup$
If that is all your source text says about when mixed partial derivatives are equal, it's time to throw it away.
$endgroup$
– user21820
Dec 17 '18 at 6:29










2 Answers
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I don't think there is any definition of pathological relating to functions (or any other mathematical concept). It's simply a word used informally to describe a function that behaves in a way you might not expect and thereby serves as a counterexample to some claim you might think was true. But a function one person finds pathological because it's "weird" (that's not defined either) in relation to his studies/interests might be uninteresting to another person, because it doesn't offer anything in relation to his studies/interests.






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    0












    $begingroup$

    You can think pathological as counterintuitive. Like everywhere continuous but nowhere differentiable function, uncountalbe null set, banach-tarski paradox. And it's not the rigorous concept, so it's weird to say finding out some function is pathological or not.






    share|cite|improve this answer









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      2 Answers
      2






      active

      oldest

      votes








      2 Answers
      2






      active

      oldest

      votes









      active

      oldest

      votes






      active

      oldest

      votes









      1












      $begingroup$

      I don't think there is any definition of pathological relating to functions (or any other mathematical concept). It's simply a word used informally to describe a function that behaves in a way you might not expect and thereby serves as a counterexample to some claim you might think was true. But a function one person finds pathological because it's "weird" (that's not defined either) in relation to his studies/interests might be uninteresting to another person, because it doesn't offer anything in relation to his studies/interests.






      share|cite|improve this answer









      $endgroup$


















        1












        $begingroup$

        I don't think there is any definition of pathological relating to functions (or any other mathematical concept). It's simply a word used informally to describe a function that behaves in a way you might not expect and thereby serves as a counterexample to some claim you might think was true. But a function one person finds pathological because it's "weird" (that's not defined either) in relation to his studies/interests might be uninteresting to another person, because it doesn't offer anything in relation to his studies/interests.






        share|cite|improve this answer









        $endgroup$
















          1












          1








          1





          $begingroup$

          I don't think there is any definition of pathological relating to functions (or any other mathematical concept). It's simply a word used informally to describe a function that behaves in a way you might not expect and thereby serves as a counterexample to some claim you might think was true. But a function one person finds pathological because it's "weird" (that's not defined either) in relation to his studies/interests might be uninteresting to another person, because it doesn't offer anything in relation to his studies/interests.






          share|cite|improve this answer









          $endgroup$



          I don't think there is any definition of pathological relating to functions (or any other mathematical concept). It's simply a word used informally to describe a function that behaves in a way you might not expect and thereby serves as a counterexample to some claim you might think was true. But a function one person finds pathological because it's "weird" (that's not defined either) in relation to his studies/interests might be uninteresting to another person, because it doesn't offer anything in relation to his studies/interests.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Dec 7 '18 at 9:03









          HenrikHenrik

          6,03792030




          6,03792030























              0












              $begingroup$

              You can think pathological as counterintuitive. Like everywhere continuous but nowhere differentiable function, uncountalbe null set, banach-tarski paradox. And it's not the rigorous concept, so it's weird to say finding out some function is pathological or not.






              share|cite|improve this answer









              $endgroup$


















                0












                $begingroup$

                You can think pathological as counterintuitive. Like everywhere continuous but nowhere differentiable function, uncountalbe null set, banach-tarski paradox. And it's not the rigorous concept, so it's weird to say finding out some function is pathological or not.






                share|cite|improve this answer









                $endgroup$
















                  0












                  0








                  0





                  $begingroup$

                  You can think pathological as counterintuitive. Like everywhere continuous but nowhere differentiable function, uncountalbe null set, banach-tarski paradox. And it's not the rigorous concept, so it's weird to say finding out some function is pathological or not.






                  share|cite|improve this answer









                  $endgroup$



                  You can think pathological as counterintuitive. Like everywhere continuous but nowhere differentiable function, uncountalbe null set, banach-tarski paradox. And it's not the rigorous concept, so it's weird to say finding out some function is pathological or not.







                  share|cite|improve this answer












                  share|cite|improve this answer



                  share|cite|improve this answer










                  answered Dec 7 '18 at 9:07









                  Lee.HWLee.HW

                  1137




                  1137















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