What is the norm of the partition used for?












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I'm confused on what purpose the norm has. I know that it defines the maximum length of the widest subinterval in a partition.



But what use do we have from defining $||P||$ to be $max[Delta t_1, Delta t_2, … ,Delta t_n] $??



Because usually don't we just use the regular n-th partitions anyways? Idk, my textbook just defines the norm once, and then never uses it again so I'm a little confused.










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  • $begingroup$
    In some sense it measures the coarseness of the partition, like distinguishing between boulders, rocks, pebbles, sand. Everything in the partition is no bigger than the norm.
    $endgroup$
    – MPW
    Jan 15 at 21:52










  • $begingroup$
    So if the norm was like 5, then the function has the potential to be "coarse" as you say, because each width could be 1,2,3, 4.23, etc.... but if the norm was like 1, the widths don't have as wide of a range?
    $endgroup$
    – ming
    Jan 15 at 22:05










  • $begingroup$
    Probably the main thing is that if the norm goes to zero, then so do the lengths of all intervals in the partition.
    $endgroup$
    – MPW
    Jan 15 at 22:23
















0












$begingroup$


I'm confused on what purpose the norm has. I know that it defines the maximum length of the widest subinterval in a partition.



But what use do we have from defining $||P||$ to be $max[Delta t_1, Delta t_2, … ,Delta t_n] $??



Because usually don't we just use the regular n-th partitions anyways? Idk, my textbook just defines the norm once, and then never uses it again so I'm a little confused.










share|cite|improve this question









$endgroup$












  • $begingroup$
    In some sense it measures the coarseness of the partition, like distinguishing between boulders, rocks, pebbles, sand. Everything in the partition is no bigger than the norm.
    $endgroup$
    – MPW
    Jan 15 at 21:52










  • $begingroup$
    So if the norm was like 5, then the function has the potential to be "coarse" as you say, because each width could be 1,2,3, 4.23, etc.... but if the norm was like 1, the widths don't have as wide of a range?
    $endgroup$
    – ming
    Jan 15 at 22:05










  • $begingroup$
    Probably the main thing is that if the norm goes to zero, then so do the lengths of all intervals in the partition.
    $endgroup$
    – MPW
    Jan 15 at 22:23














0












0








0





$begingroup$


I'm confused on what purpose the norm has. I know that it defines the maximum length of the widest subinterval in a partition.



But what use do we have from defining $||P||$ to be $max[Delta t_1, Delta t_2, … ,Delta t_n] $??



Because usually don't we just use the regular n-th partitions anyways? Idk, my textbook just defines the norm once, and then never uses it again so I'm a little confused.










share|cite|improve this question









$endgroup$




I'm confused on what purpose the norm has. I know that it defines the maximum length of the widest subinterval in a partition.



But what use do we have from defining $||P||$ to be $max[Delta t_1, Delta t_2, … ,Delta t_n] $??



Because usually don't we just use the regular n-th partitions anyways? Idk, my textbook just defines the norm once, and then never uses it again so I'm a little confused.







calculus






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asked Jan 15 at 21:48









mingming

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4606












  • $begingroup$
    In some sense it measures the coarseness of the partition, like distinguishing between boulders, rocks, pebbles, sand. Everything in the partition is no bigger than the norm.
    $endgroup$
    – MPW
    Jan 15 at 21:52










  • $begingroup$
    So if the norm was like 5, then the function has the potential to be "coarse" as you say, because each width could be 1,2,3, 4.23, etc.... but if the norm was like 1, the widths don't have as wide of a range?
    $endgroup$
    – ming
    Jan 15 at 22:05










  • $begingroup$
    Probably the main thing is that if the norm goes to zero, then so do the lengths of all intervals in the partition.
    $endgroup$
    – MPW
    Jan 15 at 22:23


















  • $begingroup$
    In some sense it measures the coarseness of the partition, like distinguishing between boulders, rocks, pebbles, sand. Everything in the partition is no bigger than the norm.
    $endgroup$
    – MPW
    Jan 15 at 21:52










  • $begingroup$
    So if the norm was like 5, then the function has the potential to be "coarse" as you say, because each width could be 1,2,3, 4.23, etc.... but if the norm was like 1, the widths don't have as wide of a range?
    $endgroup$
    – ming
    Jan 15 at 22:05










  • $begingroup$
    Probably the main thing is that if the norm goes to zero, then so do the lengths of all intervals in the partition.
    $endgroup$
    – MPW
    Jan 15 at 22:23
















$begingroup$
In some sense it measures the coarseness of the partition, like distinguishing between boulders, rocks, pebbles, sand. Everything in the partition is no bigger than the norm.
$endgroup$
– MPW
Jan 15 at 21:52




$begingroup$
In some sense it measures the coarseness of the partition, like distinguishing between boulders, rocks, pebbles, sand. Everything in the partition is no bigger than the norm.
$endgroup$
– MPW
Jan 15 at 21:52












$begingroup$
So if the norm was like 5, then the function has the potential to be "coarse" as you say, because each width could be 1,2,3, 4.23, etc.... but if the norm was like 1, the widths don't have as wide of a range?
$endgroup$
– ming
Jan 15 at 22:05




$begingroup$
So if the norm was like 5, then the function has the potential to be "coarse" as you say, because each width could be 1,2,3, 4.23, etc.... but if the norm was like 1, the widths don't have as wide of a range?
$endgroup$
– ming
Jan 15 at 22:05












$begingroup$
Probably the main thing is that if the norm goes to zero, then so do the lengths of all intervals in the partition.
$endgroup$
– MPW
Jan 15 at 22:23




$begingroup$
Probably the main thing is that if the norm goes to zero, then so do the lengths of all intervals in the partition.
$endgroup$
– MPW
Jan 15 at 22:23










1 Answer
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If you know that a function is Riemann integrable, then you can limit yourself to use the regular partitions. But if you want to prove that a function is Riemann integrable, you need all partitions, not just the regular ones. It is in this process that the norm of the partition is useful.






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    1 Answer
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    1 Answer
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    $begingroup$

    If you know that a function is Riemann integrable, then you can limit yourself to use the regular partitions. But if you want to prove that a function is Riemann integrable, you need all partitions, not just the regular ones. It is in this process that the norm of the partition is useful.






    share|cite|improve this answer









    $endgroup$


















      1












      $begingroup$

      If you know that a function is Riemann integrable, then you can limit yourself to use the regular partitions. But if you want to prove that a function is Riemann integrable, you need all partitions, not just the regular ones. It is in this process that the norm of the partition is useful.






      share|cite|improve this answer









      $endgroup$
















        1












        1








        1





        $begingroup$

        If you know that a function is Riemann integrable, then you can limit yourself to use the regular partitions. But if you want to prove that a function is Riemann integrable, you need all partitions, not just the regular ones. It is in this process that the norm of the partition is useful.






        share|cite|improve this answer









        $endgroup$



        If you know that a function is Riemann integrable, then you can limit yourself to use the regular partitions. But if you want to prove that a function is Riemann integrable, you need all partitions, not just the regular ones. It is in this process that the norm of the partition is useful.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Jan 15 at 22:40









        Julián AguirreJulián Aguirre

        69.5k24297




        69.5k24297






























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