Trapezoidal

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

float f(float x)
{
    return 1 / (x+1);
}

int main()
{
    float a, b, epsilon = powf(10, -5), II, IO, h, s;
    int n = 1, counter=1;
    printf("a=>");
    scanf("%f", &a);
    printf("b=>");
    scanf("%f", &b);
    //printf("epsilon=>");
    //scanf("%f", &epsilon);
    II = (f(a) + f(b)) * (b - a) / 2;
    do {
        n *= 2;
        h = (b - a) / n;
        IO = II;
        s = 0;
        for (int i = 1; i <= n - 1; i++)
            s += f(a + i * h);
        II = (f(a) + 2 * s + f(b)) * h / 2;
        counter++;
    } while (fabs(II - IO) >= epsilon);
    printf("The value of the integral part with precision %f is %f in %d steps.\n", epsilon, II, counter);
    system("pause");
    return 0;
}