lab1 v5

#include <iostream>
#include <math.h>

using namespace std;

double f(double x);
double integral(double start, double end, double epsil, double (*fun)(double));
double integral(double start, double end, double epsil, int &n, double (*fun)(double));

int main()
{
    double a, b, result1, result2, epsil;
    int n = 0;
    cout << "Please, enter start, end: ";
    cin >> a >> b;
    cout << "Enter epsil: ";
    cin >> epsil;
    result1 = integral(a, b, epsil, f);
    result2 = integral(a, b, epsil, n, f);
    cout << "Integral1 = " << result1 << endl;
    cout << "Integral2 = " << result2 << " and n = " << n << endl;

    return 0;
}

double f(double x)
{
    return x + 4 / (x + 0.3) - sin(x) - 3;
}

double integral(double start, double end, double epsil, double (*fun)(double))
{
    double result = 0;
    for (double x = start; x<end; x+=epsil)
        result += fabs(fun(x+epsil/2));
    return result*epsil;
}

double integral(double start, double end, int count, double (*fun)(double))
{
    double dx = (end - start) / count, result = 0;
    for (int i = 0; i < count; i++)
        result += fabs(fun(start + dx * i + dx/2));
    return result*dx;
}
double integral(double start, double end, double epsil, int &n, double (*fun)(double))
{
    double result1, result2;
    n = 10;
    do {
        result1 = integral(start, end, n, fun);
        result2 = integral(start, end, 2*n, fun);
        n *= 2;
    } while (fabs(result1 - result2) > epsil*3);
    n /= 2;
    return result1;
}