Polynomial with infinit-degree Sec 11.8 POWER SERIES Example Polynomial of degree n Power Series (Polynomial with infinit-degree) Example Power Series Polynomial with infinit-degree

at each x  infinite series POWER SERIES Example Polynomial of degree n Power Series (Polynomial with infinite-degree) Example Power Series at each x  infinite series

POWER SERIES Example Polynomial of degree n Power Series Example (Polynomial with infinit-degree) Example domain is the set of all x for which the series converges.

POWER SERIES Polynomial of degree n Example Power Series Example Polynomial centered at a or a polynomial about a Example Polynomial centered at 1 Polynomial centered at 0 Power Series centered at a Example Remark: even when

POWER SERIES Theorem: Theorem: 1 1 2 2 3 3 Example Definition: 3 centered at a Theorem: Theorem: there are only three possibilities: there are only three possibilities: The series converges only when 1 1 The series converges for all 2 2 There is a positive number R such that the series There is a positive number R such that 3 3 converges if converges if diverges if Example Definition: The number R in case is called the radius of convergence of the power series. 3

POWER SERIES Definition: 3 Theorem: Theorem: 1 1 2 2 3 3 Example The number R in case is called the radius of convergence of the power series. 3 Theorem: Theorem: there are only three possibilities: there are only three possibilities: Radius of convergence The series converges only when 1 1 The series converges for all 2 2 There is a positive number R such that the series 3 converges if 3 diverges if Example

POWER SERIES Theorem: How to find R = radius of convergence there are only three possibilities: Radius of convergence Find: 1 1 Find: 2 (L is a function of x only) 2 3 Use ratio test: 3

Final-082 POWER SERIES 1 2 3 How to find R = radius of convergence (L is a function of x only) Use ratio test: 3

POWER SERIES Theorem: 1 1 2 2 3 3 Example Example Example Example How to find R = radius of convergence there are only three possibilities: Radius of convergence Find: 1 1 Find: 2 (L is a function of x only) 2 3 Use ratio test: 3 Example Example Find the radius of convergence Find the radius of convergence Example Example (Bessel function of order 0) Find the radius of convergence Find the radius of convergence

POWER SERIES Theorem: Theorem: 1 1 2 2 3 3 Example Remark: 3 divg there are only three possibilities: there are only three possibilities: Radius of convergence The series converges only when 1 1 The series converges for all 2 2 There is a positive number R such that the series 3 3 converges if diverges if Example Remark: case say nothing about the endpoints 3 converges if diverges if divg convg divg

POWER SERIES Definition: Definition: 3 Theorem: Theorem: 1 1 2 2 3 3 The interval of convergence is the interval that consists of all values of x for which the series converges. The number R in case is called the radius of convergence of the power series. 3 Theorem: Theorem: there are only three possibilities: Interval of convergence there are only three possibilities: Radius of convergence 1 1 2 2 3 3 Remark: Example endpoint of the interval, that is, , anything can happen—the series might converge at one or both endpoints or it might diverge at both endpoints. Remark: Thus in case there are four possibilities for the interval of convergence: 3

POWER SERIES 1 2 3 1 2 How to find R = radius of convergence Find: (L is a function of x only) Use ratio test: 3 How to find interval of convergence Find R: 1 Study convg at endpoints: a+R and a-R 2

POWER SERIES Final-092

POWER SERIES Final-081

POWER SERIES Final-082

POWER SERIES convg divg Example Example Example Example (Bessel function of order 0) Find the interval of convergence Find the interval of convergence Example Example Find the interval of convergence Find the interval of convergence

POWER SERIES Final-081

DIFFERENTIATION Theorem: 1 2 Example: POWER SERIES has radius of convergence 2 radius of convergence of is R Example: radius of convergence of is 1 radius of convergence of is ??

Sec 11.9 & 11.10: TAYLOR AND MACLAURIN INTEGRATION Theorem: 1 has radius of convergence 2 radius of convergence of is R Example: radius of convergence of is 1 radius of convergence of is ?? Remark: Although Theorem says that the radius of convergence remains the same when a power series is differentiated, this does not mean that the interval of convergence remains the same. It may happen that the original series converges at an endpoint, whereas the differentiated series diverges there.

Operations on Power Series Intersection of interval of convergence Add: Subtrac:

Delay: After 11.10 POWER SERIES Operations on Power Series Intersection of interval of convergence Multiplicat: Example: Find the first 3 terms of

POWER SERIES Example: Find the first 3 terms of