labs-3semester/Lab1/lab.c

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

double poly(double x) {
	return 0.25 * pow(x,3) + x - 1.2502;
}


double alg(double x) {
	return pow(x,4) + 3 * pow(x,3) - 9 * x - 9;
}


double algbrake(double x) {
	return -(pow(x,4) + 3 * pow(x,3) - 9 * x - 9)/(x-1.5);
}

double secant(double(*f)(double), double xk, double xk1, double eps, int N) {
	double xk2;
	double fxk = f(xk);
	double fxk1 = f(xk1);
	for (int i = 1; i < N; i++)
	{
		if (fabs(xk1 - xk) < eps) {
			break;
		}
		xk2 = xk1 - fxk1 * ((xk1 - xk) / (fxk1 - fxk));
		xk = xk1;
		fxk = fxk1;
		xk1 = xk2;
		fxk1 = f(xk2);
	}
	return xk2;
}

double bisection(double(*f)(double), double a, double b, double eps, int N) {
	double fa = f(a);
	double fb = f(b);
	double c;
	if (fa * fb >= 0) {
		return 0;
	}
	for (int i = 0; i < N; i ++) 
	{   
		c = 0.5 * (a + b);
        
		if ((b - a) < 2*eps) {
			return c;
		}

		double fc = f(c);

		if (fa * fc > 0) {
			a = c;
			fa = fc;
		}

		else {
			b = c;
			fb = fc;
		}
	}
	return c;
}

void PrintResult (double eps) {
    double x1 = secant(algbrake, 1.51, 2, eps, 1000);
	double x2 = bisection(algbrake, 1.51, 2, eps, 1000);
    printf("Function with a brake: \n");
    printf("Secant method: \n");
	printf("x = %lf\n", x1);
	printf("Bisection method: \n");
	printf("x = %lf\n", x2);
	
    double x3 = secant(alg, 1, 2, eps, 1000);
	double x4 = bisection(alg, 1, 2, eps, 1000);
    printf("Algebraic function: \n");
    printf("Secant method: \n");
	printf("x = %lf\n", x3);
	printf("Bisection method: \n");
	printf("x = %lf\n", x4);

    double x5 = secant(poly, 0, 2, eps, 1000);
	double x6 = bisection(poly, 0, 2, eps, 1000);
    printf("Polynomial: \n");
    printf("Secant method: \n");
	printf("x = %lf\n", x5);
	printf("Bisection method: \n");
	printf("x = %lf\n", x6);
}


int main() {
	PrintResult(pow(10, -5));
}