# Computation of complex integral over circle [duplicate]

I am beginning Mathematica user. Please show me the syntax on how to compute the following complex integral in Mathematica:

$\int_{|z-2i|=10} \frac{dz}{z(1-e^{-5z})}$

What I really want is a subroutine that takes $f$ - my function and $c$ - my circle and compute the following complex integral. Samples in documentation force me to alter $f$ every time. But calculation insets relies on residues, so I want to have clean syntax.

Thanks a lot for your help!

• The documentation here has examples for Integral along a complex line, Along a piecewise linear contour in the complex plane and also Along a circular contour in the complex plane reference.wolfram.com/language/ref/Integrate.html – Lotus May 18 '17 at 11:55
• Hello. Thanks for the comment. I do not think your reference is practical. Imagine my that analytic express of $f$ has 30 instances of $z$. I do not want to covert every $z$ to parametric form. What I want is to have one unified function for different function $f$ and different contour $c$. – Hedgehog May 18 '17 at 12:06
• If you're actually computing residues, why not use Residue[]? – J. M.'s torpor May 18 '17 at 12:20
• What code have you written for your f? – Daniel Lichtblau May 18 '17 at 14:23
• Possible duplicate of Paths integrals in the complex plane. Also this can be instructive How to calculate contour integrals with Mathematica? – Artes May 18 '17 at 14:31

## 1 Answer

Try this:

    z = 2*I + 10*E^(I*t);
NIntegrate[10/(z + (1 - E^(-5*z))), {t, 0, 2 \[Pi]}]

(*   2.07045 - 0.0177716 I  *)


Have fun!

• Thanks for your reply. However, I do not need numeric value, I need symbolic one. – Hedgehog May 18 '17 at 12:00
• Then try Integrate instead, but I doubt that it will work. – Alexei Boulbitch May 18 '17 at 12:14