/// <summary>
/// arccos(x)를 반환함
/// </summary>
/// <param name="x">-1≤x≤1인 실수</param>
public static double Acos(double x)
{
if (x < -1 || x > 1)
{
return(Double.NaN);
}
double min = 0, max = Math.PI;
double mid = Math.PI / 2;
double cos = Trigonometric.Cos(mid);
while (max - min >= 1.0 / Int32.MaxValue)
{
if (cos < x)
{
max = mid;
}
else
{
min = mid;
}
mid = (max + min) / 2;
cos = Trigonometric.Cos(mid);
}
return(mid);
}
/// <summary>
/// arctan(x)를 반환함
/// </summary>
public static double Atan(double x)
{
if (Double.IsPositiveInfinity(x))
{
return(+Math.PI * 0.5);
}
if (Double.IsNegativeInfinity(x))
{
return(-Math.PI * 0.5);
}
double min = -Math.PI * 0.5, max = +Math.PI * 0.5;
double mid = 0;
double tan = Trigonometric.Tan(mid);
while (max - min >= 1.0 / Int32.MaxValue)
{
if (tan > x)
{
max = mid;
}
else
{
min = mid;
}
mid = (max + min) / 2;
tan = Trigonometric.Tan(mid);
}
return(mid);
}
/// <summary>
/// arcsin(x)를 반환함
/// </summary>
/// <param name="x">-1≤x≤1인 실수</param>
public static double Asin(double x)
{
if (x < -1 || x > 1)
{
return(Double.NaN);
}
double min = -Math.PI * 0.5, max = +Math.PI * 0.5;
double mid = 0;
double sin = Trigonometric.Sin(mid);
while (max - min >= 1.0 / Int32.MaxValue)
{
if (sin > x)
{
max = mid;
}
else
{
min = mid;
}
mid = (max + min) / 2;
sin = Trigonometric.Sin(mid);
}
return(mid);
}
