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Holomorphic functions and the Cauchy-Riemann equations

What complex differentiability demands, and why it is so restrictive.

f = u + iv is holomorphic when u_x = v_y and u_y = −v_x. Then u and v are harmonic and f is infinitely differentiable. Picture it: z² = (x² − y²) + i(2xy): the level curves of the real and imaginary parts cross at right angles. Think it: the derivative at a point is a rotation-and-scaling, so holomorphic maps preserve angles (conformal).

Үйлдэл · derivative of x^2 - y^2 wrt x

Calculus · Derivatives

Differentiate x^2 - y^2

\frac{d}{dx}\left[x^{2} - y^{2}\right]

Алхам алхмаар

  1. \frac{d}{dx}\left[x^{2} - y^{2}\right]

    Start from the derivative to compute.

  2. \frac{d}{d x} x^{2} + \frac{d}{d x} \left(- y^{2}\right)

    Sum rule: differentiate term by term.

  3. 2 x + \frac{d}{d x} \left(- y^{2}\right)

    Power rule: (xⁿ)′ = n·xⁿ⁻¹ with n = 2.

  4. 2 x

    The derivative of a constant is 0.

Хариулт
f'(x) = 2 x

Одоо та Даалгавар сонго, эсвэл бич, эсвэл зур. Бүх алхам, зураг, хариулт нь асуулт асуух хүртэл нуугдаж байдаг.

Өөрийнхөө ажлыг үргэлжлүүл

Үнэгүй бүртгэл нь хичээл бүрийн тэмдэглэл, төгссөн хичээл, шийдсэн даалгаврын тэмдэглэл, энэ хуудсан дээр асууж болох багшийг нэгтгэж өгдөг. Математик нь бүртгэлтэй, бүртгэлтэйгүй хэн бүхэнд нээлттэй.

Бүртгүүлэх Нэвтрэх

Энд ашигласан тэмдэгтүүд

Бүх тодорхойлолт, зураг, үсгийн утгыг харахын тулд ямар ч тэмдэгтийг дарна уу.

Яаж: Holomorphic functions and the Cauchy-Riemann equations

  1. Start from the derivative to compute.
  2. Sum rule: differentiate term by term.
  3. Power rule: (xⁿ)′ = n·xⁿ⁻¹ with n = 2.
  4. The derivative of a constant is 0.

Хүмүүс асуудаг асуултууд

Why is complex differentiability so much stronger than real?

The limit must be the same from every direction in the plane, not just two. That forces the Cauchy-Riemann equations, which in turn force infinitely many derivatives and a convergent Taylor series.

What is a residue?

The coefficient of 1/(z − a) in the Laurent series at a singularity a. The residue theorem says a contour integral equals 2πi times the sum of the residues inside, which evaluates many real integrals in one line.

Бүх зүйл Complex Analysis

The complex plane and Euler's formulaContour integrals and the residue theoremPower series and analytic continuation