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ZWMath›Complex analysis›Series and residues›Isolated singularity›ZW-ISOLATED-SINGULARITY-002
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AreaAnalysisCourseComplex analysisTopicSeries and residues
Complex numbers7
  • Complex number
  • Complex conjugate
  • Modulus of a complex number
  • Polar form
  • Complex nth root
  • De Moivre's formula
  • Topology of the complex plane
Functions and limits6
  • Complex function
  • Complex limit
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  • Complex exponential
  • Complex logarithm
  • Complex trigonometric functions
Analytic functions5
  • Complex derivative
  • Cauchy-Riemann equations
  • Holomorphic function
  • Harmonic function
  • Möbius transformation
Complex integration7
  • Curve and contour
  • Contour integral
  • Cauchy-Goursat theorem
  • Complex primitive
  • Cauchy integral formula
  • Liouville's theorem
  • Fundamental theorem of algebra
Series and residues7
  • Complex Taylor series
  • Laurent series
  • Isolated singularity
  • Zero and pole
  • Residue
  • Residue theorem
  • Real integral by residues

Exercise · ZW-ISOLATED-SINGULARITY-002 · ★☆☆ Basic

What kind of singularity does \(e^{1/z}\) have at \(z=0\)?

Choose one option.

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  • D. Essential

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Explanation

\(e^{1/z}=\sum z^{-k}/k!\) has infinitely many negative powers with nonzero coefficient; that is an essential singularity.

Study Complex analysis in ZWMath →

Review the concept: Isolated singularity

An isolated singularity of a function \(f\) is a point \(z_0\) where \(f\) is not holomorphic but is holomorphic on a punctured disc \(0<|z-z_0|<r\) around it.

More practice problems: isolated singularity

  • ZW-ISOLATED-SINGULARITY-001 What kind of singularity does (sin z)/(z) have at z=0?
  • ZW-ISOLATED-SINGULARITY-003 What kind of singularity does 1z^2+1 have at z=i?
  • ZW-ISOLATED-SINGULARITY-004 The singularity of (cos z-1)/(z^2) at z=0 is removable. What value must f(0) take to remove it?
  • ZW-ISOLATED-SINGULARITY-005 What is the order of the pole of 1z^2(z-1) at z=0?
  • ZW-ISOLATED-SINGULARITY-006 If |f| is bounded on a punctured disc 0<|z-z_0|<r, what kind of isolated singularity does f have at…
  • ZW-ISOLATED-SINGULARITY-007 Which of these functions has at z=0 a singular point that is NOT an isolated singularity?
  • ZW-ISOLATED-SINGULARITY-008 Classify the singularity of (z)/(sin z) at z=π.
  • ZW-ISOLATED-SINGULARITY-009 Classify the singularity of zsin 1z at z=0.

← ZW-ISOLATED-SINGULARITY-001 ZW-ISOLATED-SINGULARITY-003 →

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