Bad math

gistfile1.cs

using MathNet.Numerics;
using System;
using System.Numerics;

namespace ConsoleApplication21
{
  class Program
  {
    static void Main(string[] args)
    {
      Complex c1 = -1234000000;
      Complex c2 = 1234000000;

      Console.WriteLine(c1.InverseSine());
      Console.WriteLine(c2.InverseCosine());

      Console.WriteLine(Complex.Asin(c1));
      Console.WriteLine(Complex.Acos(c2));

      /* output
      (NaN, Infinity)
      (NaN, Infinity)
      (0, 16.3983624574988)
      (1.5707963267949, 16.3983624574988)
      */

      // see: https://connect.microsoft.com/VisualStudio/feedback/details/790328/complex-asin-and-complex-acos-in-system-numerics-yields-incorrect-results#details
    }
  }
}