интеграл

#include <stdio.h>
#include <math.h>
double f(double x);
double f(double x) {
    return sqrt(1 + pow(x, 5));
}

double composite_simpson(double a, double b);
double composite_simpson(double a, double b) {
    return (b - a) * (f(a) + 4 * f(0.5 * (a + b)) + f(b)) / 6;
}

double adaptive_simpson(double a, double b, double eps);
double adaptive_simpson(double a, double b, double eps) {
    double I;
    double I2;

    if (fabs(b - a) < eps)
        return 0;

    I = composite_simpson(a, b);
    I2 = composite_simpson(a, 0.5 * (a + b)) + composite_simpson(0.5 * (a + b), b);

 //   printf("Int [%lf, %lf] I = %lf I2 = %lf\n", a, b, I, I2);

    if (fabs(I - I2) < eps * (b - a))
        return I2;

    return adaptive_simpson(a, 0.5 * (a + b), eps) + adaptive_simpson(0.5 * (a + b), b, eps);
}

double func(double x, double alpha, double eps);
double func(double x, double alpha, double eps) {
    return adaptive_simpson(-x, x, eps) - (3-alpha/3);
}

double result(double alpha, double eps);
double result(double alpha, double eps) {
    double a, b, x;
    if ((3-alpha/3) >= 0) {
        a = 0;
        b = 1;
    }
    else {
        a = -1;
        b = 0;
    }

    if (func(a, alpha, eps) * func(b, alpha, eps) > 0)
        return NAN;
    while (b - a > eps) {
        x = (a + b)/2;


 //       printf("[%lf, %lf] f(a)=%lf f(b)=%lf\n", a, b, func(a, alpha, eps), func(b, alpha, eps));

        if (func(x, alpha, eps) * func(b, alpha, eps) < 0) {
            a = x;
        }

        else {
            b = x;
        }
    }
    return a;
}

int main(void) {
    double alpha;
    double eps;
    double x = 0;

    printf ("enter parametr: \n");

    if (scanf("%lf", &alpha) != 1) {
    printf ("wrong znachenie!\n");
    return -1;
    }

    printf ("enter epsilon:\n");

    if (scanf("%lf", &eps) != 1) {
    printf ("wrong znach!\n");
    return -1;
    }

    x = result(alpha, eps);

    printf("x = %lf\n", x);

    return 0;

}