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Power series and analytic continuation

Radius of convergence, the identity theorem, and extending ζ(s) beyond its series.

A holomorphic function equals its Taylor series on the largest disc avoiding singularities. Two holomorphic functions agreeing on a small set agree everywhere they are both defined, so a function can be extended uniquely, which is how ζ(s) exists at s = −1 (and equals −1/12). Picture it: the geometric series 1/(1 − x) converging inside |x| < 1, though the function lives everywhere except x = 1. Think it: this rigidity is the engine of the Riemann Hypothesis page.

Намунаи коркардашуда · taylor series of 1/(1-x)

Calculus · Taylor-Series

Taylor series of 1/(1 - x)

\frac{1}{1 - x}

Қадами ба қадам

  1. f(x) = \frac{1}{1 - x}

    Taylor series about x = 0: f(x) = Σ fᵏ(x₀)/k! · (x − x₀)ᵏ.

  2. f^{(0)}(0) = \frac{1}{1 - x}\big|_{x=0} = 1

    Derivative 0 at the centre.

  3. f^{(1)}(0) = \frac{1}{\left(1 - x\right)^{2}}\big|_{x=0} = 1

    Derivative 1 at the centre.

  4. f^{(2)}(0) = - \frac{2}{\left(x - 1\right)^{3}}\big|_{x=0} = 2

    Derivative 2 at the centre.

  5. f^{(3)}(0) = \frac{6}{\left(x - 1\right)^{4}}\big|_{x=0} = 6

    Derivative 3 at the centre.

  6. f^{(4)}(0) = - \frac{24}{\left(x - 1\right)^{5}}\big|_{x=0} = 24

    Derivative 4 at the centre.

  7. f^{(5)}(0) = \frac{120}{\left(x - 1\right)^{6}}\big|_{x=0} = 120

    Derivative 5 at the centre.

  8. x^{5} + x^{4} + x^{3} + x^{2} + x + 1

    Assemble the terms up to degree 5.

Ҷавоби ҷавобро нишон диҳед
x^{5} + x^{4} + x^{3} + x^{2} + x + 1 + O((x-0)^{6})

Ҳоло шумо Масъаларо интихоб кунед, ё ки онро навишта ё кашед. Ҳар қадам, тасвир, ҷавоб то он даме, ки шумо пурсед, пинҳон мешавад.

Кор кардан

Дар ҳисоби ройгон ба ҳар як дарс қайдҳо илова карда мешаванд, қайди он, ки шумо чӣ кор кардаед, масъалаҳои ҳалшуда дар як ҷо ва муаллиме, ки шумо метавонед дар бораи ин саҳифа пурсед. Математика барои ҳама кушода аст, хоҳ ворид шуда бошад ё на.

Бақайдгирӣ Ворид шудан

Символы, используемые здесь

Барои муайянкунии пурраи маъно, тасвир ва маънои ҳар як ҳарф дар он, ба ҳар як аломат пахш кунед.

Чӣ тавр: Power series and analytic continuation

  1. Taylor series about x = 0: f(x) = Σ fᵏ(x₀)/k! · (x − x₀)ᵏ.
  2. Derivative 0 at the centre.
  3. Derivative 1 at the centre.
  4. Derivative 2 at the centre.
  5. Derivative 3 at the centre.
  6. Derivative 4 at the centre.
  7. Derivative 5 at the centre.
  8. Assemble the terms up to degree 5.

Саволҳои маъмул

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.

& Иловаи забон Complex Analysis

The complex plane and Euler's formulaHolomorphic functions and the Cauchy-Riemann equationsContour integrals and the residue theorem