/// <summary>
/// Уточняет значение x до указанной точности
/// </summary>
/// <param name="originX">Исходное значение x</param>
/// <param name="accuracy">Точность</param>
/// <param name="f">Функция</param>
/// <param name="itCount">Количество итераций</param>
public static double ClarificationTangent(double originX, double accuracy, NolinearFunction f, out int itCount)
{
double
lastX,
newX = originX,
lastAccuracy = Double.PositiveInfinity;
itCount = 0;
do
{
lastX = newX;
newX = lastX - f(lastX) / Derivative(lastX, f);
var currentAccuracy = Math.Abs(lastX - newX);
if (currentAccuracy > lastAccuracy)
{
throw new Exception("The sequence diverges");
}
lastAccuracy = currentAccuracy;
itCount++;
} while (lastAccuracy > accuracy);
return(newX);
}
private static double Derivative(double x, NolinearFunction f, double interval = 0.000001)
{
return((f(x + interval / 2) - f(x - interval / 2)) / interval);
}
/// <summary>
/// Уточняет значение x методом хорд, в пределах указанных границ
/// </summary>
/// <param name="border1">Первая граница</param>
/// <param name="border2">Вторая граница</param>
/// <param name="accuracy">Точность</param>
/// <param name="f">Функция</param>
/// <param name="itCount">Количество итераций</param>
public static double ClarificationChords(double border1, double border2, double accuracy, NolinearFunction f, out int itCount)
{
bool IsEqualSign(double val1, double val2) => (val1 * val2 > 0);
if (IsEqualSign(f(border1), f(border2)))
{
throw new Exception("Wrong borders");
}
double poolValue;
double poolX;
itCount = 0;
do
{
poolX = border1 - f(border1) * (border2 - border1) / (f(border2) - f(border1));
poolValue = f(poolX);
itCount++;
if (IsEqualSign(poolValue, f(border1)))
{
border1 = poolX;
continue;
}
if (IsEqualSign(poolValue, f(border2)))
{
border2 = poolX;
continue;
}
throw new Exception("Sign error");
} while (poolValue > accuracy);
return(poolX);
}
