Calculating Radius of Convergence for Power Series | Limsupreme Challenge

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In summary, the radius of convergence for a power series is the distance from the center of the series to the closest point where the series is defined. It is determined by the limit of the absolute value of the ratio between consecutive coefficients as the terms in the series approach infinity. To calculate the radius of convergence, the ratio test or the root test can be used. The radius of convergence determines the size of the interval of convergence, which is the range of values for which the series will converge. It cannot be negative and is directly related to the accuracy of a power series approximation. A larger radius of convergence results in a more accurate approximation, but may not be accurate for all values in the interval of convergence.
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betty2301
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Homework Statement


Calculate the radius of convergence of [itex]\sum_{n=0}^\infty a_{n}^{2}z^{n}[/itex]
let [itex]\sum_{n=0}^\infty a_{n}z^{n}RADIUS R[/itex]

Homework Equations


[itex]\limsup|a_n|^{\frac{1}{n}}=\limsup |\frac{a_{n+1}}{a_n}|[/itex]

The Attempt at a Solution


the latex is killin me please help....
 
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  • #2
Again this should be straightforward. Just compute one of the limits under relevant equations using the coefficients for your new power series and relate this to R.
 

FAQ: Calculating Radius of Convergence for Power Series | Limsupreme Challenge

What is the definition of radius of convergence for a power series?

The radius of convergence for a power series is the distance from the center of the series to the closest point where the series is defined. It is represented by the variable R and is determined by the limit of the absolute value of the ratio between consecutive coefficients as the terms in the series approach infinity.

How do you calculate the radius of convergence for a power series?

To calculate the radius of convergence, you can use the ratio test or the root test. The ratio test compares the absolute value of the ratio between consecutive coefficients to a limit, while the root test compares the nth root of the absolute value of the coefficients to a limit. Whichever test gives a finite result will provide the radius of convergence.

What is the relationship between the radius of convergence and the interval of convergence for a power series?

The radius of convergence determines the size of the interval of convergence for a power series. The interval of convergence is the range of values for which the series will converge, and it extends from the center of the series to a distance of R in both directions. So, the larger the radius of convergence, the larger the interval of convergence will be.

Can the radius of convergence be negative?

No, the radius of convergence for a power series cannot be negative. It represents a distance and therefore must be positive. If the radius of convergence is negative, it means that the series is not convergent at any point.

How does the radius of convergence affect the accuracy of a power series approximation?

The radius of convergence is directly related to the accuracy of a power series approximation. The larger the radius of convergence, the more terms in the series are included, and the more accurate the approximation will be. However, a larger radius of convergence also means a wider interval of convergence, so the approximation may not be accurate for all values in that interval.

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