Conditionally convergent integral












4












$begingroup$


It is known that in a conditionally convergent series, the terms can be rearranged so as to output any desired value. Thus, a conditionally convergent series is said to be undefined.



My question is about the following integral:
$intlimits_{ - infty }^infty {{{sin left( x right)} over x}dx} $



It's known that this integral is conditionally convergent: it converges, but no absolutely.



Can one say that if ${a_n}buildrel {n to infty } over
longrightarrow infty $
and ${b_n}buildrel {n to infty } over
longrightarrow - infty $
that the value of
$$mathop {lim }limits_{n to infty } intlimits_{{b_n}}^{{a_n}} {{{sin left( x right)} over x}dx} $$
depends on the choice of the sequences ${a_n},{b_n}$ ?



I have experimented a bit in wolfram alpha but no matter what I tried, the result was $pi $.



I do remember hearing and in fact I've read also here:



Is there a rearrangement theorem for conditionally convergent improper integrals?



That the value of the conditionally convergent integral depends on the rearrangement.










share|cite|improve this question









$endgroup$

















    4












    $begingroup$


    It is known that in a conditionally convergent series, the terms can be rearranged so as to output any desired value. Thus, a conditionally convergent series is said to be undefined.



    My question is about the following integral:
    $intlimits_{ - infty }^infty {{{sin left( x right)} over x}dx} $



    It's known that this integral is conditionally convergent: it converges, but no absolutely.



    Can one say that if ${a_n}buildrel {n to infty } over
    longrightarrow infty $
    and ${b_n}buildrel {n to infty } over
    longrightarrow - infty $
    that the value of
    $$mathop {lim }limits_{n to infty } intlimits_{{b_n}}^{{a_n}} {{{sin left( x right)} over x}dx} $$
    depends on the choice of the sequences ${a_n},{b_n}$ ?



    I have experimented a bit in wolfram alpha but no matter what I tried, the result was $pi $.



    I do remember hearing and in fact I've read also here:



    Is there a rearrangement theorem for conditionally convergent improper integrals?



    That the value of the conditionally convergent integral depends on the rearrangement.










    share|cite|improve this question









    $endgroup$















      4












      4








      4





      $begingroup$


      It is known that in a conditionally convergent series, the terms can be rearranged so as to output any desired value. Thus, a conditionally convergent series is said to be undefined.



      My question is about the following integral:
      $intlimits_{ - infty }^infty {{{sin left( x right)} over x}dx} $



      It's known that this integral is conditionally convergent: it converges, but no absolutely.



      Can one say that if ${a_n}buildrel {n to infty } over
      longrightarrow infty $
      and ${b_n}buildrel {n to infty } over
      longrightarrow - infty $
      that the value of
      $$mathop {lim }limits_{n to infty } intlimits_{{b_n}}^{{a_n}} {{{sin left( x right)} over x}dx} $$
      depends on the choice of the sequences ${a_n},{b_n}$ ?



      I have experimented a bit in wolfram alpha but no matter what I tried, the result was $pi $.



      I do remember hearing and in fact I've read also here:



      Is there a rearrangement theorem for conditionally convergent improper integrals?



      That the value of the conditionally convergent integral depends on the rearrangement.










      share|cite|improve this question









      $endgroup$




      It is known that in a conditionally convergent series, the terms can be rearranged so as to output any desired value. Thus, a conditionally convergent series is said to be undefined.



      My question is about the following integral:
      $intlimits_{ - infty }^infty {{{sin left( x right)} over x}dx} $



      It's known that this integral is conditionally convergent: it converges, but no absolutely.



      Can one say that if ${a_n}buildrel {n to infty } over
      longrightarrow infty $
      and ${b_n}buildrel {n to infty } over
      longrightarrow - infty $
      that the value of
      $$mathop {lim }limits_{n to infty } intlimits_{{b_n}}^{{a_n}} {{{sin left( x right)} over x}dx} $$
      depends on the choice of the sequences ${a_n},{b_n}$ ?



      I have experimented a bit in wolfram alpha but no matter what I tried, the result was $pi $.



      I do remember hearing and in fact I've read also here:



      Is there a rearrangement theorem for conditionally convergent improper integrals?



      That the value of the conditionally convergent integral depends on the rearrangement.







      improper-integrals






      share|cite|improve this question













      share|cite|improve this question











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      share|cite|improve this question










      asked Dec 7 '18 at 8:52









      zokomokozokomoko

      157214




      157214






















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          $begingroup$

          The limit is $pi$ irrespective of what those sequences are. It is a standard fact that $lim _{tto infty}int_0^{t} frac {sin , x} x , dx=pi/2$ from which my claim follows.






          share|cite|improve this answer









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            1 Answer
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            $begingroup$

            The limit is $pi$ irrespective of what those sequences are. It is a standard fact that $lim _{tto infty}int_0^{t} frac {sin , x} x , dx=pi/2$ from which my claim follows.






            share|cite|improve this answer









            $endgroup$


















              3












              $begingroup$

              The limit is $pi$ irrespective of what those sequences are. It is a standard fact that $lim _{tto infty}int_0^{t} frac {sin , x} x , dx=pi/2$ from which my claim follows.






              share|cite|improve this answer









              $endgroup$
















                3












                3








                3





                $begingroup$

                The limit is $pi$ irrespective of what those sequences are. It is a standard fact that $lim _{tto infty}int_0^{t} frac {sin , x} x , dx=pi/2$ from which my claim follows.






                share|cite|improve this answer









                $endgroup$



                The limit is $pi$ irrespective of what those sequences are. It is a standard fact that $lim _{tto infty}int_0^{t} frac {sin , x} x , dx=pi/2$ from which my claim follows.







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered Dec 7 '18 at 8:59









                Kavi Rama MurthyKavi Rama Murthy

                53.5k32055




                53.5k32055






























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