Thread: Trapezoidal Rule Adding Values

  1. #1
    Registered User hungrymouth's Avatar
    Join Date
    Oct 2012

    Trapezoidal Rule Adding Values

    So I want to approximate the area of the integral using the trapezoidal method. The function has limits from 1 to 2 and the function is sqrt(x^3-1)dx. So the number of rectangles this function has is 10 with the width of 1/10. This is what I have so far in my code. I have calculated from 1 to 2 with this formula and used the while loop.

    width/2[f(x)+2f(x1)+2f(x2)+2f(x3)...+f(n) and so on)

    so since the width is 1/10, It's just increasing by .1 so it's going from 1,1.1,1.2,1.3 all the way to 2

    Now that I have those values calculated. All I have to do is add all those values and divide it by width/2 which in this case is 1/20. How would I do that?

    #include "stdafx.h"
    #include <iostream>
    #include <math.h>
    using namespace std;
    int main()
        double x;
        double number;
        number = 2.0;
        for(x = 1 ; x < number ; x=x+0.1)
           cout<< "\n\n\tThe value is" << 2*sqrt(x*x*x-1);
        return 0;
    Last edited by hungrymouth; 02-25-2013 at 02:10 PM.

  2. #2
    Registered User rogster001's Avatar
    Join Date
    Aug 2006
    Liverpool UK
    Well you just store all the results in the loop in a variable?? when the loop exits you can then divide by whatever value required
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