Complex Power Series/Examples
Jump to navigation
Jump to search
Examples of Complex Power Series
Example: $\ds \sum_{n \mathop \ge 0} n z^n$
The complex power series:
- $S = \ds \sum_{n \mathop \ge 0} n z^n$
has a radius of convergence of $1$.
Example: $\ds \sum_{n \mathop \ge 0} \dfrac {3^n - 1} {2^n + 1} z^n$
Let $\sequence {a_n}$ be the sequence defined as:
- $a_n = \dfrac {3^n - 1} {2^n + 1}$
The complex power series:
- $S = \ds \sum_{n \mathop \ge 0} a_n z^n$
has a radius of convergence of $\dfrac 2 3$.
Example: $\ds \sum_{n \mathop \ge 0} \dfrac {\paren {2 n}!} {\paren {n!}^2} z^n$
Let $\sequence {a_n}$ be the sequence defined as:
- $a_n = \dfrac {\paren {2 n}!} {\paren {n!}^2} z^n$
The complex power series:
- $S = \ds \sum_{n \mathop \ge 0} a_n z^n$
has a radius of convergence of $\dfrac 1 4$.
Example: $\ds \sum_{n \mathop \ge 0} \dfrac {\cos i n} {n^2} z^n$
Let $\sequence {a_n}$ be the sequence defined as:
- $a_n = \dfrac {\cos i n} {n^2} z^n$
The complex power series:
- $S = \ds \sum_{n \mathop \ge 0} a_n z^n$
has a radius of convergence of $\dfrac 1 e$.