Lab4(DNR)

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

const double K = 22.5;
const double L = 7.5;

double A(double x);
double B(double x);
double Y(double a, double b);

int main(void)
{
    double x[3] = { 0.324, 1.426, -0.414 };

    printf("\tLab4\n");

    for (int o = 0; o < 3; o++)
    {
        if (A(x[o]) == NULL)
        {
            printf("a = invalid x, must be more than 0, where x = %lf\n", x[o]);
        }
        else {
            printf("a = %lf, where x = %lf\n", A(x[o]), x[o]);
        }

        if (B(x[o]) == NULL)
        {
            printf("b = Invalid x, must be more than 0, where x = %lf\n", x[o]);
        }
        else {
            printf("b = %lf, where x = %lf\n", B(x[o]), x[o]);
        }

        if (Y(A(x[o]), B(x[o])) == NULL)
        {
            printf("y = Invalid x, must be more than 0, where x = %lf\n", x[o]);
        }
        else {
            printf("y = %lf, where x = %lf\n", Y(A(x[o]), B(x[o])), x[o]);
        }
    }
}

double A(double x)
{
    if (x > 0)
    {
        double a = pow(pow(K, -1 / 2) - L * sqrt(x + 2.84), 2);
        return a;
    }
    else {
        return NULL;
    }
}

double B(double x)
{
    if (x > 0)
    {
        double b = -log10(x) + exp(x);
        return b;
    }
    else {
        return NULL;
    }
}

double Y(double a, double b)
{
    if (a == 0 || b == 0)
    {
        return NULL;
    }
    else {
        if (a > b)
        {
            double y = 4 * a + 3 * b / pow(a, 2) + pow(b, 2);
            return y;
        }
        else if(a <= b)
        {
            double y = fabs(a - b);
            return y;
        }
    }
}