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Complex Analysis

Functions of a complex variable -- where differentiability becomes a much stronger, more geometric idea, and a single theorem (Cauchy's) unlocks results no real-variable argument can reach.

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1 The complex plane πŸ”’

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  • The complex plane and regions ~16 min
  • Distance, circles, and disks ~16 min
  • Lines, half-planes, and loci ~16 min
  • Inequalities and regions ~18 min
  • Connectedness and domains ~16 min

2 Complex functions, limits, and continuity πŸ”’

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  • Functions of a complex variable ~16 min
  • Limits of complex functions ~18 min
  • Limits via real and imaginary parts ~18 min
  • Continuity ~16 min
  • Limits and the point at infinity ~16 min

3 Complex differentiation and the Cauchy-Riemann equations πŸ”’

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  • The complex derivative ~16 min
  • Analytic, holomorphic, and entire functions ~14 min
  • The Cauchy-Riemann equations β€” necessary conditions ~18 min
  • The Cauchy-Riemann equations β€” sufficient conditions ~16 min
  • Cauchy-Riemann in polar coordinates ~15 min
  • Zero derivative implies constant ~14 min

4 Harmonic functions πŸ”’

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  • Harmonic functions and Laplace's equation ~16 min
  • Harmonic conjugates ~18 min
  • The maximum principle and mean value property ~16 min
  • The identity theorem ~16 min
  • The Schwarz reflection principle ~15 min

5 Elementary Complex Functions πŸ”’

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  • The complex exponential function ~20 min
  • The logarithm and its branches ~22 min
  • Complex powers ~20 min
  • Trigonometric and hyperbolic functions ~22 min
  • Inverse trigonometric and hyperbolic functions ~20 min

6 Complex Integration πŸ”’

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  • Contours and parametrization ~20 min
  • Contour integrals ~25 min
  • Properties of contour integrals and the ML inequality ~25 min
  • Antiderivatives and path independence ~25 min
  • The fundamental theorem for contour integrals ~20 min

7 Cauchy's Theorem and Its Consequences πŸ”’

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  • The Cauchy-Goursat theorem ~24 min
  • Simply and multiply connected domains ~20 min
  • Contour deformation ~20 min
  • The Cauchy integral formula ~24 min
  • The derivative formula ~22 min
  • Liouville's theorem and the Fundamental Theorem of Algebra ~22 min
  • The maximum modulus principle ~22 min

8 Power Series and Taylor Series πŸ”’

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  • Convergence of complex sequences and series ~22 min
  • Taylor's theorem for analytic functions ~22 min
  • Uniform convergence and term-by-term calculus ~20 min
  • Uniqueness of power series representations ~18 min
  • Multiplying and dividing power series ~20 min

9 Laurent Series and Singularities πŸ”’

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  • Laurent's theorem ~24 min
  • Isolated singularities -- removable, pole, and essential ~24 min
  • The pole order and residue shortcut formula ~24 min
  • Zeros of analytic functions ~22 min
  • Behavior near isolated singularities ~22 min

10 The Residue Theorem πŸ”’

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  • The residue ~20 min
  • Cauchy's residue theorem ~22 min
  • Residue at infinity ~20 min
  • Computing residues, several methods ~22 min

11 Applications of Residues πŸ”’

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  • Real improper integrals via semicircular contours ~24 min
  • Trigonometric integrals via the unit circle ~22 min
  • Indented contours and principal values ~24 min
  • Jordan's lemma ~24 min
  • The argument principle ~24 min
  • RouchΓ©'s theorem ~26 min
  • Inverse Laplace transforms via residues ~26 min

12 Mobius Transformations and Conformal Mapping πŸ”’

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  • Linear transformations and inversion ~18 min
  • MΓΆbius transformations ~20 min
  • Conformal mapping and angle preservation ~18 min
  • The elementary mapping catalogue ~18 min
  • The Riemann sphere and the extended complex plane ~18 min
  • Schwarz's lemma ~18 min
  • The Schwarz-Pick theorem ~20 min
  • Harmonic conjugates revisited ~20 min

13 Applications of Conformal Mapping πŸ”’

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  • Steady-state temperature and electrostatic potential ~24 min
  • Two-dimensional fluid flow ~24 min
  • The Schwarz-Christoffel transformation ~26 min
  • The Poisson integral formula and the Dirichlet problem ~28 min
  • The Neumann problem ~20 min

14 Analytic Continuation πŸ”’

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  • Natural boundaries ~20 min
  • The identity theorem, revisited ~18 min
  • Continuation along a curve ~20 min
  • Branch points and why continuation can fail ~20 min

15 Advanced Topics: The Gamma Function and Complex Dynamics πŸ”’

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  • The Gamma function ~22 min
  • The functional equation and the reflection formula ~24 min
  • An introduction to complex dynamics ~20 min
  • Julia sets and the Mandelbrot set, qualitatively ~22 min