Gauss Legendre numerical intergration

In summary, Gauss Legendre numerical integration is a method for approximating a definite integral using a weighted sum of function values at specific points. The values of the weights and points are determined by the number of intervals, n, used in the method. In this example, with n=2, the values of α and r are substituted into the formula to find the approximate value of the integral. The values for other n are not used in this particular calculation.
  • #1
Sadeq
107
0
Gauss Legendre numerical intergration
The attachment file contain solved example
i don't know how he subsitute and why a2=2 done disappear in the answer
please expalin in details
 

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  • Handout4.pdf.pdf
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  • #2
n=2
so
a2=1
 
  • #3
lurflurf said:
n=2
so
a2=1

What about a1=2
doent apper
could u explain more pls
 
  • #4
sure, we have from the handout and Gauss Legendre numerical integration
I=α1α1r12e^r1
1α2r12e^r2
2α1r22e^r1
2α2r22e^r2
now since n=2 we use
r1=-1/sqrt(3)~-0.57735026918962576450914878050196
r2=1/sqrt(3)~0.57735026918962576450914878050196
α1=1~1.000000000000000000000000000000000
αsub]2[/sub]=1~1.000000000000000000000000000000000

So just substitute in the values to find I
I=(4/3)cosh(1/sqrt(3))
=(1.000000000000000000000000000000000)(1.000000000000000000000000000000000)(-0.57735026918962576450914878050196)2e^-0.57735026918962576450914878050196
+(1.000000000000000000000000000000000)(1.000000000000000000000000000000000)(-0.57735026918962576450914878050196)2e^0.57735026918962576450914878050196
+(1.000000000000000000000000000000000)(1.000000000000000000000000000000000)(0.57735026918962576450914878050196)2e^-0.57735026918962576450914878050196
+(1.000000000000000000000000000000000)(1.000000000000000000000000000000000)(0.57735026918962576450914878050196)2e^0.57735026918962576450914878050196
=1.5617973919398203851893261344599

notice that only the values of α and r for n=2 are used
The values of α and r for other n are not used
In the handout all the ones were implied
 
Last edited:
  • #5
thank you brother
 

What is Gauss Legendre numerical integration?

Gauss Legendre numerical integration is a method used to approximate the definite integral of a function. It involves dividing the interval of integration into smaller subintervals and using a weighted sum of function values at specific points within each subinterval to estimate the integral.

How does Gauss Legendre numerical integration work?

The method works by using a predetermined set of points and weights, known as the Gauss-Legendre quadrature points and weights, within each subinterval. These points and weights are chosen to minimize the error in the approximation. The integral is then estimated by taking the weighted sum of function values at these points within each subinterval.

What are the advantages of using Gauss Legendre numerical integration?

Gauss Legendre numerical integration is known for its high accuracy and efficiency, making it a popular choice for approximating integrals. It also has a wide range of applicability, as it can be used for both smooth and non-smooth functions.

What are the limitations of Gauss Legendre numerical integration?

One limitation of this method is that it can only be used for one-dimensional integrals. It also requires the function to be evaluated at specific points, which can be computationally expensive for functions with a large number of variables.

How does Gauss Legendre numerical integration compare to other numerical integration methods?

Gauss Legendre numerical integration is generally considered to be more accurate than other numerical integration methods, such as the trapezoidal rule or Simpson's rule. However, it may not be as efficient for certain types of functions, such as oscillatory or highly irregular functions.

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