public static void Main(string[] args)
{
double[] x, y;
x = new double[] { 0, PI *0.25, PI *0.5, PI *0.75, PI };
y = new double[x.Length];
for (int i = 0; i < x.Length; i++)
{
y[i] = Cos(x[i]); // y is cos(x)
}
double z;
int step = 5; //number of steps between two points
interpolate.quadratic q = new interpolate.quadratic(x, y);
for (int i = 0; i < x.Length - 1; i++)
{
for (int j = 0; j < step; j++)
{
z = x[i] + j * (x[i + 1] - x[i]) / step;
WriteLine($"{z} {q.spline(z)} {Cos(z)} {q.derivative(z)} {-Sin(z)} {q.integral(z)} {Sin(z)}");
}
}
}
