power series
A power series is a series of the form
∞∑k=0ak(x-x0)k, |
with ak,x0∈ℝ or ∈ℂ. The ak are called the coefficients and x0 the center of the power series. a0 is called the constant term.
Where it converges the power series defines a function, which can thus be represented by a power series. This is what power series are usually used for.
Every power series is convergent at least at x=x0 where it converges to a0. In addition it is absolutely and uniformly convergent in the region {x∣|x-x0|<r}, with
r=lim inf |
It is divergent for every with . For no general predictions can be made. If , the power series converges absolutely and uniformly for every real or complex The real number is called the radius of convergence of the power series.
Examples of power series are:
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Taylor series
, for example:
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Power series have some important :
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If a power series converges for a then it also converges for all with .
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Also, if a power series diverges for some then it diverges for all with .
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For Power series can be added by adding coefficients and multiplied in the obvious way:
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(Uniqueness) If two power series are equal and their are the same, then their coefficients must be equal.
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Power series can be termwise differentiated and integrated. These operations
keep the radius of convergence.
Title | power series |
Canonical name | PowerSeries |
Date of creation | 2013-03-22 12:32:55 |
Last modified on | 2013-03-22 12:32:55 |
Owner | azdbacks4234 (14155) |
Last modified by | azdbacks4234 (14155) |
Numerical id | 23 |
Author | azdbacks4234 (14155) |
Entry type | Definition |
Classification | msc 40A30 |
Classification | msc 30B10 |
Related topic | TaylorSeries |
Related topic | FormalPowerSeries |
Related topic | TermwiseDifferentiation |
Related topic | AbelsLimitTheorem |
Defines | constant term |