//* By peter blatcher *//
#include <stdlib.h>;
#include <stdio.h>;
#include <math.h>;

float trap(float b, float Xo, int n);
float integ(float X);

int main()
{

    float Va, Ve, difference, n, area, Fao, kCao, y, X, a, b;
    char c = n;
    n = 2;
    Fao = 0.4;
    a = 0.8;
    kCao = 0.45;
    b = 0;

    printf("\nNUMERICAL INTEGRATION PROGRAM:");
    printf("\nThis program calculates the approximate value");
    printf("\nof a function containg an integral.");
    printf("\n\n V = Fao * the integral of 1/-kCao(1-X) between 0 and Xo");
    printf("\n\nFao = %.3f mol.s^-1", Fao );
    printf("\nXo = %.3f conversion", a );
    printf("\nkCao = %.3f mol.m^-3.s^-1", kCao);
    printf("\no = %.3f conversion", b);
    printf("\t strips = %.1f", n);


      do
      {
      a = 0.8;
      b = 0.0;
      Ve = ((Fao / kCao) * (log(1 / a)));
      printf("\n\nexact Volume = %.3f m^3", Ve);
      Va = trap(b, a, n) * Fao;
      printf("\tapprox volume = %.3f", Va);
      difference = (Va - Ve);
      printf("\tdiff = %.3f", difference);
      n = 2 * n;
      }
      while (difference >= (1 * (10 ^ -4)));
      {
      printf("\n\npress return to continue.");
      getchar();
      return (0);
      }
      }

       float trap(float b, float a, int n)
      {
      float d, area, y;
      int i;
      a = 0.8;
      b = 0;
      d = (a - b) / n;
      for (i = 1; i <= (n - 1); i++);
      {
      y += (integ((b + (i * d))));
      }
      area = (d * y) + (d / 2.0) * ((integ(b))+ (integ(a)));
      return area;
      }

      float integ(float X)
      {
      float y, kCao;
      kCao = 0.45;
      y = (1 / (kCao * (1-X)));
      return y;
      }

basically im trying to write a program which will work out the exact value of the following function; V = Fao * integrand 1/kCao*(1-X) between 0 and Xo. and then work out a numerical solution using the trapezium rule and compare the two, and then work out the difference and loop until the difference is less than 1 x 10^-4. there are no errors when i compile, but the program still doesnt work properly, grrr. frustating. any help and advice would be greatly appreciated.

>> there are no errors when i compile, but the program still doesnt work properly, grrr. frustating.
Welcome to the wounderful world of computer programming ;) Sorry that I can't help you -- the math is beyond me.

>> while (difference >= (1 * (10 ^ -4)));

Is that try to raise 10 to a negative power ? Doesn't that produce an imaginary number (which are not supported by C or C++ native languages)

You might want to check out some of the boost library math function

[edit]I checked with google and found that negative exponents don't do what I thought. So just ignore my dumb question above. See -- I said I was math impaired :) [/edit]

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