- #1
fred_91
- 39
- 0
Homework Statement
I want to compute the following integral
[itex]I=\int_0^1 f(x) dx[/itex]
for a function f(x) such that the integral I cannot be evaluated analytically.
f(x) is a known function.
Therefore we want to obtain I numerically. To do this we want to use the Trapezium method with uniform steps for x.
Then after that we need to compute the convergence rate.
Homework Equations
Using the trapezium method, we will split the nodes for x using equidistant steps [itex]x_0,x_1,x_2,...x_N[/itex]
In general, we have
[itex]I=\int_a^b f(x) dx = \frac{b-a}{N}\left( f(x_0)+2f(x_1)+2f(x_2)+ 2f(x_3)+...+ 2f(x_{N-1}) +f(x_n) \right)[/itex]
Aitken's extrapolation formula can be written as:
[itex]\overline{I}=I_i+\frac{(I_{i+1}-I_i)^2}{2I_{i+1}-I_i-I_{i+2}}[/itex]
for 3 consecutive points: [itex]I_{i},I_{i+1},I_{i+2}[/itex].
The Attempt at a Solution
In our case, a=0, b=1. We will take 3 cases for N: N=25, N=50, N=100.
Therefore, we will have 3 approximations: [itex]I_1, I_2, I_3[/itex] corresponding to N=25, 50, 100 respectively.
Now we can find a good approximation to the real value using Aitken's approximation:
[itex] \overline{I}=I_1+\frac{(I_2-I_1)^2}{2I_2-I_1-I_3}[/itex]
However, how does this help us to compute the convergence rate?
Any ideas or guidance is very much appreciated.
Thank you.