Calculate Complex Integrals with Series of Sin Z

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The discussion focuses on calculating complex integrals using the series expansion of sin(z) around a closed contour C, specifically the unit circle defined by z = e^(iθ) for 0 ≤ θ < 2π. Participants clarify that the series expansion for sin(z) is sin(z) = z - z³/3! + z⁵/5! - …, which is essential for evaluating the integral ∫z^k sin(z)dz. The consensus indicates that most integrals will evaluate to zero, except for one significant term, simplifying the analysis despite the infinite series involved.

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By parameterizing the curve (not by Cauchy's theorem) and using the series of sin z, nd
the value of
∫z^k sin(z)dz around a closed Contour C where C is the unit circle z=e^(iθ), for 0≤θ<2π

What do they mean by using series of sin z ? I mean if I expand it .. I get e^(iθ)- e^(3iθ)/3! ---
and so on ..Not sure what Iam meant to do with that since its an infinite series ..Do I say for small z sinz≈z , but not sure ..

thanks
 
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hi rbnphlp! :smile:
rbnphlp said:
What do they mean by using series of sin z ? I mean if I expand it .. I get e^(iθ)- e^(3iθ)/3! ---
and so on ..

they mean sinz = z - z3/3! + z5/5! - …

(learn it … also cosz = 1 - z2/2! + z4/4! - … :wink:)
Not sure what Iam meant to do with that since its an infinite series ..

(i haven't tried it :redface:, but …)

my guess is that all the integrals are going to be 0 except for one …

if so, it won't matter that there's an infinite number of them! :biggrin:
 

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