Newton.cpp

#include <iostream>
#include <math.h>
using namespace std;
float a, b, E, Dx, Ep, x;
int i;
float f(float x) {
	return   tan(x) - ((tan(x)*tan(x)*tan(x) + 1) / 3) + 0.2*tan(x)*tan(x)*tan(x)*tan(x)*tan(x);
}
float fp(float x) {
	return (f(x + Dx) - f(x)) / Dx;
}
float f2p(float x) {
	return (fp(x + Dx) - fp(x)) / Dx;
}
int main() {
	cout << "Enter limit a, b and accuracy E\n";
	cout << "a =";
	cin >> a;
	cout << "b =";
	cin >> b;
	cout << "E =";
	cin >> E;
	Dx = E / 1000;
	Ep = fabs(x - b);
	x = b;
	if (f(x)*f2p(x)<0) {
		cout << "Tabulate the function, please/n";
		system("pause");
	}
	else {
		i = 0;
		while (fabs(Ep) > E) {
			x = x - f(x) / fp(x);
			Ep = fabs(x - b);
			b = x;
			i = i + 1;
			cout << i << " x =" << x;
			cout << " f(x) =" << f(x) << endl;
		} 
	}
	system("pause");
	return 0;
}