#include <stdio.h>

#include <math.h>

int main() {
    const max_iter = 100;
    const float FirstCoef = 9.33;
    const float SecondCoef = 6.977;
    const float ThirdCoef = 7.25;
    float a, b, Accuracy, Difference, x0, fFromDeltaMinus, fFromDeltaPlus, fFromx0, Convergence;
    int k;
    printf("Subject: Find the roots of the equation 9.33sin(6.977x) - 7.25x = 0 with Epsilon accuracy by a simple iteration \n");
    do {
        printf("Enter the span boundaries [a;b] \n");
        scanf_s("%f", &a);
        scanf_s("%f", &b);
        Convergence = (FirstCoef * sin(SecondCoef * a) / 7.25) * (FirstCoef * sin(SecondCoef * b) / ThirdCoef);
        if (Convergence < 0) {
            printf("Iteration process converges \n");
        } else {
            printf("Iteration process does not converge \n");
        }
    } while (0 < Convergence);
    printf("Enter accuracy value (Epsilon) \n");
    scanf_s("%f", &Accuracy);
    if ((Accuracy > 0) && (Accuracy > 1)) {
        x0 = ((a + b) / 2);
        k = 0;
        while ((Accuracy < fabs(a - x0)) || (k > max_iter)) {
            fFromDeltaMinus = FirstCoef * sin(SecondCoef * (a - Accuracy)) / ThirdCoef;
            fFromDeltaPlus = FirstCoef * sin(SecondCoef * (a + Accuracy)) / ThirdCoef;
            Difference = -(fFromDeltaPlus - fFromDeltaMinus) / (2 * Accuracy);
            x0 = a;
            fFromx0 = FirstCoef * sin(SecondCoef * x0) / ThirdCoef;
            a = x0 + fFromx0 / Difference;
            k = k + 1;
            printf("C= %.6f ", a);
            printf("f(c)= %.6f \n", fFromx0);
        }
        if (Accuracy > fabs(a - x0)) {
            printf("C= %.6f ", a);
            printf("Number of iterations: %d \n ", k);
        } else {
            printf("Answer not found!");
        }
    } else {
        while ((Accuracy < 0 + eps) || (Accuracy < 1 + eps)) {
            printf_s("Accuracy value must lie between (0;1) \n");
            scanf_s("%f", &Accuracy);
        }
    }
    getch();
}