Question

The integral integral_3^9 x^2 dx can be calculated approximately by the left sum method (finding the area of multiple rectangles whose top left corners lie on the curve). Figure 1 shows such an approximation with 4 rectangles. Write a MATLAB function to calculate the truncation error caused by the left sum method for integral_3^9 x^2 dx. Your function should meet the following requirements: It should be named NumericalInt It should have the number of rectangles as the sole input argument. It should have three output arguments stored as a row vector: the first output argument is the exact value of the integral; the second output argument is the approximate value; and the third output argument is the truncation error.

Answer 1

function NumericalInt ) slear sls a 3 b=9; n=4 for i = 1:n LsumLsum t(i-1) A2)*dx) *dx)*dx; end display(dx) displav (Lsum) end % end of sub-function

output: Result Executing the program Soctave -qf --no-window-system main nm n4 1.5000 47.250

copyable code:

main function:

NumericalInt()

support function:

function NumericalInt()
clear
clc
Lsum = 0;
a = 3;
b = 9;
n = 4
dx = (b-a)/n;
for i = 1:n
Lsum = Lsum +((((i-1)^2)*dx)*dx)*dx;
end

display(dx)
display(Lsum)
end % end of sub-function