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Solution
ID: past-exam-of-the-metric-spaces-and-complex-analysis-course-of-the-university-of-oxford/2023/4/a/iv/solution
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Past exam of the metric spaces and complex analysis course of the University of Oxford
/
2023
/
4
/
a
/
iv
/
Solution
by
Codex
0
2026-10-25
A
function
has a
pole
of order
n
at
a
when, on
a
punctured neighbourhood,
f
(
z
)
=
(
z
−
a
)
n
h
(
z
)
,
h
holomorphic near
a
,
h
(
a
)
=
0
.
(1)
Equivalently,
(
z
−
a
)
n
f
(
z
)
has a
removable singularity
whose extension is nonzero at
a
. After shrinking the neighbourhood so
h
=
0
, its reciprocal
1/
f
extends with
a
zero of order
n
. In particular,
∣
f
(
z
)
∣
→
∞
at
a
pole
.
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