В общем есть задание
. Есть код к этой задаче(вставил в конце), но он не совсем правильно работает, он считает Рунге Кутта 4го порядка, а надо сделать 2го. Заранее благодарю за помощь). Вот ручное решение задачи:
#include "stdafx.h"
#include
using namespace std;
const double eps = 1e-3;
double k = 0;
double f(double x)
{
return pow(x, 5) - pow(x, 3) - 3;
}
double runge(double X, double Y)
{
return cos(k*X + Y) + (3 * (X-Y));
}
int main()
{
double a, b, c;
double dy;
double n = 100;
double h;
double k1, k2, k3, k4;
double *X = new double[n];
double *Y = new double[n];
cout << "Delenie otrezka popolam" << endl << endl;
cout << "Vvedite a: "; cin >> a; cout << endl;
cout << "Vvedite b: "; cin >> b; cout << endl;
do
{
c = (a + b) / 2;
if (f(b) * f(c) < 0)
a = c;
else
b = c;
cout << "c = " << c << endl;
} while (abs(f(c)) > eps);
cout << "c = " << c << endl << endl;
k = c;
cout << "k = " << k << endl << endl;
{
cout << "Runge-Kutta 2 poryadka" << endl << endl;
cout << "Vvedite a: "; cin >> a; cout << endl;
cout << "Vvedite b: "; cin >> b; cout << endl;
cout << "Vvedite n: "; cin >> n; cout << endl;
h = 0,1;
cout << "Shag = " << h; cout << endl; cout << endl;
X[0] = a; Y[0] = 0.0;
for (int i = 1; i <= n; i++)
{
X = a + i*h;
}
for (int i = 1; i <= n; i++)
{
cout << "X&" << i << "]=" << X << " " << endl;
}
cout << endl; cout << endl;
for (int i = 1; i <= n; i++)
{
k1 = Y(i)+h/2*runge(X, Y);
cout << "k1 = " << k1 << " " << endl;
k2 = h*runge(X + h / 2, Y + k1 / 2);
cout << "k2 = " << k2 << " " << endl;
k3 = h*runge(X + h / 2, Y + k2 / 2);
cout << "k3 = " << k3 << " " << endl;
k4 = h*runge(X + h, Y + k3);
cout << "k4 = " << k4 << " " << endl;
dy = (k1 + 2 * k2 + 2 * k3 + k4) * (1.00 / 6.00);
cout << "dy = " << dy << " " << endl;
Y = Y + dy; cout << "Y&" << i << "]= " << Y << " " << endl;
}
return 0;
}
}