Chebshev polynomial approximation

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SUMMARY

The discussion focuses on using Chebyshev polynomial approximation to find the coefficients for the function f(x) = (x + 2)ln(x + 2) in MATLAB. The user encountered issues with the command double(int(...)), which failed to provide numerical values and returned a warning about the explicit integral. The suggested solution involves substituting x = cos(θ) to eliminate the singularity, allowing for a more effective computation of the integral.

PREREQUISITES
  • Understanding of Chebyshev polynomials and their properties.
  • Familiarity with MATLAB programming and its symbolic toolbox.
  • Knowledge of numerical integration techniques.
  • Basic calculus, particularly integration of logarithmic functions.
NEXT STEPS
  • Explore MATLAB's symbolic toolbox for advanced integration techniques.
  • Learn about Chebyshev polynomial properties and their applications in approximation.
  • Study numerical methods for handling singularities in integrals.
  • Investigate the use of substitutions in integral calculus, specifically trigonometric substitutions.
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Students and researchers in mathematics, particularly those focusing on numerical analysis and polynomial approximations, as well as MATLAB users seeking to enhance their skills in symbolic computation.

sbashrawi
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Homework Statement



Hi every body

I am triyng to find a polynolial approximation to the function: f(x)= (x+2)ln(x+2)
using the chebyshev polynomials,
the idea is to use MATLAB to find the coeefficients of the approximation poly.
using the comand double(int(...))
but this command doesn't give me any numerical value
what I got was:
>> int((x+2)*log(x+2)*(1-x^2)^-0.5,-1,1)
Warning: Explicit integral could not be found.
ans =
int((log(x + 2)*(x + 2))/(1 - x^2)^(1/2), x = -1..1)
>>
and if I use double(int(...)) an error message shows up
Any help pls

Homework Equations





The Attempt at a Solution

 
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Consider the substitution x=\cos(\theta) and note that T_k(x) = \cos(k \,\theta). This should remove the singularity.
 

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