singularities( Essential and removable) of a complex function. The 2019 Stack Overflow Developer Survey Results Are InComplex analysis removable singularitiesRemovable singularities of a holomorphic functionRemovable Singularities for a exponential type functionProof Essential Singularities are IsolatedHow does squaring a function affect it's removable singularities?Essential singularities and polesCauchy Goursat and removable singularitiesRemovable singularities and an entire functionapplication of Riemann's theorem on removable singularitiesCan a meromorphic function have removable singularities?

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singularities( Essential and removable) of a complex function.



The 2019 Stack Overflow Developer Survey Results Are InComplex analysis removable singularitiesRemovable singularities of a holomorphic functionRemovable Singularities for a exponential type functionProof Essential Singularities are IsolatedHow does squaring a function affect it's removable singularities?Essential singularities and polesCauchy Goursat and removable singularitiesRemovable singularities and an entire functionapplication of Riemann's theorem on removable singularitiesCan a meromorphic function have removable singularities?










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enter image description here



I have some doubts on this question.
I think the first and second are false. As for the others I'm not sure.










share|cite|improve this question









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  • $begingroup$
    The first one is clearly true.
    $endgroup$
    – Saucy O'Path
    Apr 7 at 21:57










  • $begingroup$
    you are right. i meant the second and fourth.
    $endgroup$
    – Luís Cruz
    Apr 7 at 21:59















1












$begingroup$


enter image description here



I have some doubts on this question.
I think the first and second are false. As for the others I'm not sure.










share|cite|improve this question









$endgroup$











  • $begingroup$
    The first one is clearly true.
    $endgroup$
    – Saucy O'Path
    Apr 7 at 21:57










  • $begingroup$
    you are right. i meant the second and fourth.
    $endgroup$
    – Luís Cruz
    Apr 7 at 21:59













1












1








1





$begingroup$


enter image description here



I have some doubts on this question.
I think the first and second are false. As for the others I'm not sure.










share|cite|improve this question









$endgroup$




enter image description here



I have some doubts on this question.
I think the first and second are false. As for the others I'm not sure.







complex-analysis






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Apr 7 at 21:52









Luís CruzLuís Cruz

183




183











  • $begingroup$
    The first one is clearly true.
    $endgroup$
    – Saucy O'Path
    Apr 7 at 21:57










  • $begingroup$
    you are right. i meant the second and fourth.
    $endgroup$
    – Luís Cruz
    Apr 7 at 21:59
















  • $begingroup$
    The first one is clearly true.
    $endgroup$
    – Saucy O'Path
    Apr 7 at 21:57










  • $begingroup$
    you are right. i meant the second and fourth.
    $endgroup$
    – Luís Cruz
    Apr 7 at 21:59















$begingroup$
The first one is clearly true.
$endgroup$
– Saucy O'Path
Apr 7 at 21:57




$begingroup$
The first one is clearly true.
$endgroup$
– Saucy O'Path
Apr 7 at 21:57












$begingroup$
you are right. i meant the second and fourth.
$endgroup$
– Luís Cruz
Apr 7 at 21:59




$begingroup$
you are right. i meant the second and fourth.
$endgroup$
– Luís Cruz
Apr 7 at 21:59










1 Answer
1






active

oldest

votes


















1












$begingroup$

Actually, the first one is true: if the Laurent series of $f$ at $z_0$ has infinitely many non-zero terms of the type $a_n(z-z_0)^n$ with $n<0$, then the same thing occurs with $(z-z_0)^2f(z)$.



But you are right about the secnd one: it is false.



The third one is true: you are multiplying $f(z)$ by an analytic function whose domain contains $z_0$: Therefore, the essential singularity at $z_0$ remains as such.



And the fourth one is false, of course.






share|cite|improve this answer









$endgroup$












  • $begingroup$
    Thank you for your help. I meant that the second and fourth are false (my bad).
    $endgroup$
    – Luís Cruz
    Apr 7 at 22:04











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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









1












$begingroup$

Actually, the first one is true: if the Laurent series of $f$ at $z_0$ has infinitely many non-zero terms of the type $a_n(z-z_0)^n$ with $n<0$, then the same thing occurs with $(z-z_0)^2f(z)$.



But you are right about the secnd one: it is false.



The third one is true: you are multiplying $f(z)$ by an analytic function whose domain contains $z_0$: Therefore, the essential singularity at $z_0$ remains as such.



And the fourth one is false, of course.






share|cite|improve this answer









$endgroup$












  • $begingroup$
    Thank you for your help. I meant that the second and fourth are false (my bad).
    $endgroup$
    – Luís Cruz
    Apr 7 at 22:04















1












$begingroup$

Actually, the first one is true: if the Laurent series of $f$ at $z_0$ has infinitely many non-zero terms of the type $a_n(z-z_0)^n$ with $n<0$, then the same thing occurs with $(z-z_0)^2f(z)$.



But you are right about the secnd one: it is false.



The third one is true: you are multiplying $f(z)$ by an analytic function whose domain contains $z_0$: Therefore, the essential singularity at $z_0$ remains as such.



And the fourth one is false, of course.






share|cite|improve this answer









$endgroup$












  • $begingroup$
    Thank you for your help. I meant that the second and fourth are false (my bad).
    $endgroup$
    – Luís Cruz
    Apr 7 at 22:04













1












1








1





$begingroup$

Actually, the first one is true: if the Laurent series of $f$ at $z_0$ has infinitely many non-zero terms of the type $a_n(z-z_0)^n$ with $n<0$, then the same thing occurs with $(z-z_0)^2f(z)$.



But you are right about the secnd one: it is false.



The third one is true: you are multiplying $f(z)$ by an analytic function whose domain contains $z_0$: Therefore, the essential singularity at $z_0$ remains as such.



And the fourth one is false, of course.






share|cite|improve this answer









$endgroup$



Actually, the first one is true: if the Laurent series of $f$ at $z_0$ has infinitely many non-zero terms of the type $a_n(z-z_0)^n$ with $n<0$, then the same thing occurs with $(z-z_0)^2f(z)$.



But you are right about the secnd one: it is false.



The third one is true: you are multiplying $f(z)$ by an analytic function whose domain contains $z_0$: Therefore, the essential singularity at $z_0$ remains as such.



And the fourth one is false, of course.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Apr 7 at 21:58









José Carlos SantosJosé Carlos Santos

174k23133242




174k23133242











  • $begingroup$
    Thank you for your help. I meant that the second and fourth are false (my bad).
    $endgroup$
    – Luís Cruz
    Apr 7 at 22:04
















  • $begingroup$
    Thank you for your help. I meant that the second and fourth are false (my bad).
    $endgroup$
    – Luís Cruz
    Apr 7 at 22:04















$begingroup$
Thank you for your help. I meant that the second and fourth are false (my bad).
$endgroup$
– Luís Cruz
Apr 7 at 22:04




$begingroup$
Thank you for your help. I meant that the second and fourth are false (my bad).
$endgroup$
– Luís Cruz
Apr 7 at 22:04

















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