Why The Interval of f(x) is the same in Both One and Two Side Limits?












0












$begingroup$


My Question might be wired For some But It Will help me to get the idea of One Side Limits.



My Book



Recall The Definition of One Side Limits :




  • Right Hand Limit


if for every number ϵ>0 there is a number δ>0 such that



$$c<x<c+δ quadlongrightarrowquad lvert f(x)- llvert<ϵ $$




  • Lift hand Limit


if for every number ϵ>0 there is a number δ>0 such that
$$c-δ<x<c quadlongrightarrowquad lvert f(x)- llvert<ϵ $$



My Question



It Might Be weird to me That putting an Interval



$$lvert f(x)- llvert<ϵ$$



in Either One of the definitions.



Consider Right hand limit, I'm assume that we need an interval such
$$l<f(x)<l+ϵ quad$$



enter image description here



Because It's Impossible to get any value at $$c<x$$



and The same Thing for Left hand Side , we might put $$l-ϵ<f(x)<l quad$$ instead of $$l-ϵ<f(x)<l+ϵ quad$$ Since it's also impassible for $$c>x$$



enter image description here



What is the point of Use $$lvert f(x)- llvert<ϵ $$ instead of what Just I Wrote of intervals For set the interval of Epsilon?



Thanks in advance










share|cite|improve this question









$endgroup$








  • 1




    $begingroup$
    What if $f$ is decreasing?
    $endgroup$
    – Hans Lundmark
    Jan 5 at 11:01










  • $begingroup$
    Using $x>c$ does not necessarily imply $f(x) >l$. The right/left refers to values of $x$ with respect to $c$ and not to values of $f(x) $.
    $endgroup$
    – Paramanand Singh
    Jan 5 at 12:52










  • $begingroup$
    @ParamanandSingh- meaning there are cases we will have $$x>c$$ for $$|f(x)-l|<ϵ$$?! Could you give me an example for limit in this case where $$x>c$$ pointing to $$f(x)<l$$
    $endgroup$
    – Ammar Bamhdi
    Jan 6 at 0:36


















0












$begingroup$


My Question might be wired For some But It Will help me to get the idea of One Side Limits.



My Book



Recall The Definition of One Side Limits :




  • Right Hand Limit


if for every number ϵ>0 there is a number δ>0 such that



$$c<x<c+δ quadlongrightarrowquad lvert f(x)- llvert<ϵ $$




  • Lift hand Limit


if for every number ϵ>0 there is a number δ>0 such that
$$c-δ<x<c quadlongrightarrowquad lvert f(x)- llvert<ϵ $$



My Question



It Might Be weird to me That putting an Interval



$$lvert f(x)- llvert<ϵ$$



in Either One of the definitions.



Consider Right hand limit, I'm assume that we need an interval such
$$l<f(x)<l+ϵ quad$$



enter image description here



Because It's Impossible to get any value at $$c<x$$



and The same Thing for Left hand Side , we might put $$l-ϵ<f(x)<l quad$$ instead of $$l-ϵ<f(x)<l+ϵ quad$$ Since it's also impassible for $$c>x$$



enter image description here



What is the point of Use $$lvert f(x)- llvert<ϵ $$ instead of what Just I Wrote of intervals For set the interval of Epsilon?



Thanks in advance










share|cite|improve this question









$endgroup$








  • 1




    $begingroup$
    What if $f$ is decreasing?
    $endgroup$
    – Hans Lundmark
    Jan 5 at 11:01










  • $begingroup$
    Using $x>c$ does not necessarily imply $f(x) >l$. The right/left refers to values of $x$ with respect to $c$ and not to values of $f(x) $.
    $endgroup$
    – Paramanand Singh
    Jan 5 at 12:52










  • $begingroup$
    @ParamanandSingh- meaning there are cases we will have $$x>c$$ for $$|f(x)-l|<ϵ$$?! Could you give me an example for limit in this case where $$x>c$$ pointing to $$f(x)<l$$
    $endgroup$
    – Ammar Bamhdi
    Jan 6 at 0:36
















0












0








0





$begingroup$


My Question might be wired For some But It Will help me to get the idea of One Side Limits.



My Book



Recall The Definition of One Side Limits :




  • Right Hand Limit


if for every number ϵ>0 there is a number δ>0 such that



$$c<x<c+δ quadlongrightarrowquad lvert f(x)- llvert<ϵ $$




  • Lift hand Limit


if for every number ϵ>0 there is a number δ>0 such that
$$c-δ<x<c quadlongrightarrowquad lvert f(x)- llvert<ϵ $$



My Question



It Might Be weird to me That putting an Interval



$$lvert f(x)- llvert<ϵ$$



in Either One of the definitions.



Consider Right hand limit, I'm assume that we need an interval such
$$l<f(x)<l+ϵ quad$$



enter image description here



Because It's Impossible to get any value at $$c<x$$



and The same Thing for Left hand Side , we might put $$l-ϵ<f(x)<l quad$$ instead of $$l-ϵ<f(x)<l+ϵ quad$$ Since it's also impassible for $$c>x$$



enter image description here



What is the point of Use $$lvert f(x)- llvert<ϵ $$ instead of what Just I Wrote of intervals For set the interval of Epsilon?



Thanks in advance










share|cite|improve this question









$endgroup$




My Question might be wired For some But It Will help me to get the idea of One Side Limits.



My Book



Recall The Definition of One Side Limits :




  • Right Hand Limit


if for every number ϵ>0 there is a number δ>0 such that



$$c<x<c+δ quadlongrightarrowquad lvert f(x)- llvert<ϵ $$




  • Lift hand Limit


if for every number ϵ>0 there is a number δ>0 such that
$$c-δ<x<c quadlongrightarrowquad lvert f(x)- llvert<ϵ $$



My Question



It Might Be weird to me That putting an Interval



$$lvert f(x)- llvert<ϵ$$



in Either One of the definitions.



Consider Right hand limit, I'm assume that we need an interval such
$$l<f(x)<l+ϵ quad$$



enter image description here



Because It's Impossible to get any value at $$c<x$$



and The same Thing for Left hand Side , we might put $$l-ϵ<f(x)<l quad$$ instead of $$l-ϵ<f(x)<l+ϵ quad$$ Since it's also impassible for $$c>x$$



enter image description here



What is the point of Use $$lvert f(x)- llvert<ϵ $$ instead of what Just I Wrote of intervals For set the interval of Epsilon?



Thanks in advance







calculus limits






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asked Jan 5 at 8:11









Ammar BamhdiAmmar Bamhdi

325




325








  • 1




    $begingroup$
    What if $f$ is decreasing?
    $endgroup$
    – Hans Lundmark
    Jan 5 at 11:01










  • $begingroup$
    Using $x>c$ does not necessarily imply $f(x) >l$. The right/left refers to values of $x$ with respect to $c$ and not to values of $f(x) $.
    $endgroup$
    – Paramanand Singh
    Jan 5 at 12:52










  • $begingroup$
    @ParamanandSingh- meaning there are cases we will have $$x>c$$ for $$|f(x)-l|<ϵ$$?! Could you give me an example for limit in this case where $$x>c$$ pointing to $$f(x)<l$$
    $endgroup$
    – Ammar Bamhdi
    Jan 6 at 0:36
















  • 1




    $begingroup$
    What if $f$ is decreasing?
    $endgroup$
    – Hans Lundmark
    Jan 5 at 11:01










  • $begingroup$
    Using $x>c$ does not necessarily imply $f(x) >l$. The right/left refers to values of $x$ with respect to $c$ and not to values of $f(x) $.
    $endgroup$
    – Paramanand Singh
    Jan 5 at 12:52










  • $begingroup$
    @ParamanandSingh- meaning there are cases we will have $$x>c$$ for $$|f(x)-l|<ϵ$$?! Could you give me an example for limit in this case where $$x>c$$ pointing to $$f(x)<l$$
    $endgroup$
    – Ammar Bamhdi
    Jan 6 at 0:36










1




1




$begingroup$
What if $f$ is decreasing?
$endgroup$
– Hans Lundmark
Jan 5 at 11:01




$begingroup$
What if $f$ is decreasing?
$endgroup$
– Hans Lundmark
Jan 5 at 11:01












$begingroup$
Using $x>c$ does not necessarily imply $f(x) >l$. The right/left refers to values of $x$ with respect to $c$ and not to values of $f(x) $.
$endgroup$
– Paramanand Singh
Jan 5 at 12:52




$begingroup$
Using $x>c$ does not necessarily imply $f(x) >l$. The right/left refers to values of $x$ with respect to $c$ and not to values of $f(x) $.
$endgroup$
– Paramanand Singh
Jan 5 at 12:52












$begingroup$
@ParamanandSingh- meaning there are cases we will have $$x>c$$ for $$|f(x)-l|<ϵ$$?! Could you give me an example for limit in this case where $$x>c$$ pointing to $$f(x)<l$$
$endgroup$
– Ammar Bamhdi
Jan 6 at 0:36






$begingroup$
@ParamanandSingh- meaning there are cases we will have $$x>c$$ for $$|f(x)-l|<ϵ$$?! Could you give me an example for limit in this case where $$x>c$$ pointing to $$f(x)<l$$
$endgroup$
– Ammar Bamhdi
Jan 6 at 0:36












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