Laurent Series Explained | How to Determine Laurent Series | Complex Analysis #9

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Everything you need to know about Laurent Series explained. The video will contain problems on Laurent Series and how to solve them all for each Laurent Series.

The video will include concepts as:
► Definition of Laurent Series
► Principal part and Analytic part of a Laurent Series
► Convergence of the Principal part and Analytic part
► A theorem about when we can use Laurent Series
► How to determine all possible Laurent Series around some point of expansion
► How to solve Laurent Series.

LINK TO COMPLEX ANALYSIS PLAYLIST

LINK TO CANVAS

SUPPORT
Consider subscribing, liking or leaving a comment, if you enjoyed the video or if it helped you understand the subject. It really helps me a lot.

CLARIFICATION OF THE METHOD:
To determine all possible Laurent Series:
Start by marking the important points on the graph, the important points are the poles of the function and the point of expansion. The will divide the complex plan into several domains and each of these domains will have its own Laurent Series, since none of these domain will contain any poles of the function.

You may note that most of the time we only need to determine ONE of the parts (analytic or principal part) to determine the Laurent Series. This comes from the fact that both of these parts are only present (converges) if we are inside an annulus domain. If you want to determine a Laurent Series outside of a circle then you only need the principal part (since the analytic part will not converge in this domain) and if you want to determine the Laurent Series inside of a circle then you only need the Analytic part (since the principal part will not converge in this domain).

CONCEPTS FROM THE VIDEO
► Laurent Series
A Laurent Series is a specific kind of power series and is used to approximate an analytic function f(z) around some point z_0 (note that z_0 can be an isolated singularity) in the complex plane

... + (a_-3) *(z-z_0)^-3 + (a_-2) *(z-z_0)^-2 + (a_-1) *(z-z_0)^-1 + a_0 + a_1 *(z-z_0) + a_2 *(z-z_0)^2 + a_3 *(z-z_0)^3 + ...

where the coefficients a_n are determined by contour integration, but 99,9 % of the cases these are determined by geometric series. Note that: "... + (a_-3) *(z-z_0)^-3 + (a_-2) *(z-z_0)^-2" is called the principal part, while "a_0 + a_1 *(z-z_0) + a_2 *(z-z_0)^2 + a_3 *(z-z_0)^3 + ..." is called the analytic part.

►Geometric Series
A geometric series is a series with a constant ratio between successive terms. An example on a geometric series is

1/(1-w) = w^0 + w^1 + w^2 +... for abs(w) smaller than 1

which can be modified to the following

1/(1- 1/w) = (1/w)^0 + (1/w)^1 + (1/w)^2 +... for abs(w) bigger than 1

and the reason these two series are used a lot to solve these kind of problems, is because this geometric series looks pretty much like the Laurent Series we would like to obtain.

► Poles
A pole is a specific kind of singularity, the short and the most intuitive definition is that poles are points z_0 in the complex plane so that f(z_0) = g(z_0)/0, where g(z_0) =\= 0.

► Partial Fraction
The partial fraction decomposition or partial fraction expansion of a rational function is used to express the fraction as a sum of fractions with a simpler denominator.

[Link to video is coming].

TIMESTAMPS
00:00 Intro
00:13 Theorem Laurent Series
01:06 What is an Annulus domain
02:04 Good things to know
03:40 Why geometric series are the best
Examples: Determine all possible Laurent Series for the following functions
05:20 f(z) = 1/(z-2) around z=0
08:02 f(z) = 1/(z-2) around z=1
09:48 f(z) = 1/((z-1)(z-2)) around z=0

SOCIAL

SOURCES:
Fundamentals of Complex Analysis with Applications to Engineering, Science, and Mathematics: Pearson New International Edition.

HASHTAGS
#TheMathCoach #ComplexAnalysis #Complex Analysis Playlist
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This video has everything you need to understand Laurent series and solve many problems. Perfect for when your teacher is completely useless

Nightfold
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By far the best explanation of laurent series on you tube. thanks for help!

aaronstone
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My first video ever to reach 100 000+ views, I'm really happy to be able to help so many people with mathematics!

TheMathCoach
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I have a Complex Analysis exam tomorrow and this video made me understand Laurent series better than any book/notes I've read. Than you!

igragarirg
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You can't imagine how much I love you rn, you saved my complex analysis course xd

ramonmerinorojas
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Amazing explanation.
Came here completely confused — my prof didn't explain it at all — and am now as clear as I can be.
Thanks!!

shivarammani
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This is a fantastic video and explanation. The pace (much faster than Khan Academy etc) actually helps, because it forces you to pay attention and helps you soak in the concepts and approaches better. Much thanks. Do keep making videos!

pranavkrishnan
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You are my savior, there’s no video/guide on the internet as precious as this video if you’re sarching for a clear and complete explanation of Laurent Series, thanks man!

thekingsoftube
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Finding these videos was like finding a treasure, thank you so

alejandrosoto
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Wow, what an excellent video!! There are some moving parts about Laurent Series I didn’t realize until just now*, but you've cleared up my frustrations. Thank you and well done!

isaackay
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Clear and well explained, very beautiful handwriting too. Thanks for explaining what my prof cannot

hiveknight
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Exam in 5 days, keen for this playlist!

davidjohnson-mysr
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That's a really good explanation!
Concise listing of concepts and formulas, great use of colors to highlight important variables
Thanks for spending so much time in this :)

elvis_mello
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loved it !
excellent and crispy explanation ...just to the point...keep going students like me needs teacher like you 📝🙌

dhananjaymahajan
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Dude that's the loveliest most Swedish accent if I ever have heard one! :D And Thanks for the vid, exam in two days, fingers crossed!

ranani
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i had no words to describe how much i have to thank you for videos! the beast explanation ever!!!!

rodrigovelasquez
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Thank you very much for this playlist!
It helps so much! And it feels good to understand some things finally 🙏😄

balazsvajda
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Your presentation is EXTREMELY good and the concepts are also taught VERY well. I have a friendly tip though. If you could add some voice modulations or perhaps simply pause before you bring up an important or note-worthy point, it would help break the monotony. This would keep the viewers engaged. Anyway, I am grateful for finding your video. Thank you.

aneeshaavasthi
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Man thank you, Laurent series were giving me a serious headache but it's wayyyy clearer now. Also wanted to say the quality of this vid is insanely good, like props to you.

ALBAGetos
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I really hope you start making videos again, I would love to see your explanations of different topics in higher level math.

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