Laurent Expansion of sin(1-1/z)

In summary, to find the Laurent expansion of f(z) = sin(1-1/z) about z = 0, you can use the sine sum formula to write it as sin(1)cos(1/z)-cos(1)sin(1/z) and then use the Taylor's series for sine and cosine. The annulus of convergence for this expansion is given by the radius of convergence of the Taylor series for sine and cosine, which is |z| < 1.
  • #1
nicksauce
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Homework Statement


Find the Laurent expansion of [tex]f(z) = \sin(1-\frac{1}{z})[/tex] about z = 0, and state the annulus of convergence.

Homework Equations


The Attempt at a Solution


I tried doing the regular expansion of sin(z), then applying the binomial expansion on the (1-1/z)^n terms, but I can't help but feel that there's a better way to approach the problem. Any thoughts?
 
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  • #2
I would suggest that you use the sine sum formula to write it as
[tex]sin(1-\frac{1}{z})= sin(1)cos(\frac{1}{z})- cos(1)sin(\frac{1}{z})[/tex]
and then use the Taylor's series for sine and cosin.
 
  • #3
Boy don't I feel dumb. Thanks!
 
  • #4
is this sentence correct?
sin(1/z)=1/z-1/z^3*3!+1/z^5*5!+-...
for laurent series?
 

1. What is the Laurent expansion of sin(1-1/z)?

The Laurent expansion of sin(1-1/z) is a mathematical series that represents the power series expansion of the function sin(1-1/z). It can be written as a sum of infinite terms, where each term is a coefficient multiplied by a power of (1-1/z).

2. Why is the Laurent expansion of sin(1-1/z) important?

The Laurent expansion of sin(1-1/z) is important because it allows us to approximate the value of the function for any given value of z. It also helps us understand the behavior of the function near singularities, where the function is not defined.

3. How is the Laurent expansion of sin(1-1/z) derived?

The Laurent expansion of sin(1-1/z) is derived using techniques from complex analysis, such as Cauchy's integral formula and the residue theorem. These techniques involve manipulating complex numbers and integrating along specific paths in the complex plane.

4. What is the region of convergence for the Laurent expansion of sin(1-1/z)?

The region of convergence for the Laurent expansion of sin(1-1/z) is the set of all complex numbers z for which the series converges. In this case, it is the set of all z such that |z| > 1. This means that the series converges for all values of z outside the unit circle in the complex plane.

5. How is the Laurent expansion of sin(1-1/z) used in real-world applications?

The Laurent expansion of sin(1-1/z) is used in various fields of science and engineering, such as signal processing, fluid dynamics, and electromagnetism. It is also used in the analysis of physical systems with singularities, such as black holes in astrophysics. In these applications, the expansion is used to approximate the behavior of a system near singularities or to solve differential equations involving the function.

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