Matlab Quick Start 82: Series and Taylor Expansion

1.Programming Example

(1) Calculate the sum of the series, compute the power seriesxn/n!(n takes values from0 to∞) sum function

Program:

syms n x

f=x^n/factorial(n)

symsum(f,n,0,inf)

Running Result:

f =

x^n/factorial(n)

ans =

exp(x)

(2) Calculate the Taylor expansion, computef=exp(x) atx=1 with5th order approximate Taylor expansion

syms x y

f=exp(x)

taylor(f,x,’ExpansionPoint’,1,’Order’,5)

Running Result:

f =

exp(x)

ans =

exp(1) + exp(1)*(x – 1) + (exp(1)*(x – 1)^2)/2 + (exp(1)*(x – 1)^3)/6 + (exp(1)*(x – 1)^4)/24

2. Special Note

symsum is used to calculate the sum of series functions, similar to summing sequences (see article 77Matlab Quick Start Basics 77: Summing Sequences, Applications of Geometric and Arithmetic Series), a series is a function that connects the terms of a sequence with addition, typical series include positive series, alternating series, power series, Fourier series, etc.

The Symbolic Math ToolboxMatlab Quick Start 54: Symbolic Math Toolbox provides two summation functions,sum calculates the sum of elements in a matrix or vector, summing along a certain dimension,symsum calculates the sum of symbolic series, summing over a certain index, for definite series summation,symsum is faster thansum for solving, for uncertain series summation, onlysymsum can be used.

taylor is used to compute the Taylor expansion, also known as the Taylor series, the concept and expression of the Taylor series can be reviewed online, placing the formula editor here is too difficult.

[I speak for myself:freexyn, a minimalist and free style]

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