C# Math trig functions using System.Numerics.Complex type

ComplexFun.cs

using System;
using System.Numerics;

namespace MathFun
{
    /// <summary>
    /// Trig functions for Complex numbers
    /// </summary>
    /// <remarks>
    /// main reference: Schaum's Outlines: Complex Variables ISBN-13: 978-0070602304
    /// </remarks>
    public static class ComplexFun
    {
        /// <summary
        /// Inverse trigonometric functions - arccosine
        /// implemented using log form
        /// </summary>
        /// <param name="z">Complex value</param>
        /// <returns>Complex value - arccosine of z</returns>
        public static Complex acos(Complex z)
        {
            Complex res = new Complex(0.0, -1.0) *
                (Complex.Log(z + Complex.Sqrt(Complex.Pow(z, 2) - Complex.One)));

            double re = res.Real;
            double im = res.Imaginary;

            // rounding check
            if ((re - Math.Floor(re)) > 0.9999001)
            {
                res = new Complex(Math.Round(re), im);
            }

            return res;
        }
        
        
        /// <summary
        /// Inverse trigonometric functions - arccosecant
	    /// implemented using log form
        /// </summary>
        /// <param name="z">Complex value</param>
        /// <returns>Complex value - arcosecant of z</returns>
        public static Complex acsc (Complex z) 
        {
            Complex res = new Complex(0.0, -1.0) * 
                (Complex.Log(Complex.ImaginaryOne + 
                    Complex.Sqrt(Complex.Pow(z, 2))) / z);

            double re = res.Real;
            double im = res.Imaginary;

            // rounding check
            if ((re - Math.Floor(re)) > 0.9999001)
            {
                res = new Complex(Math.Round(re), im);
            }

            return res;
        }

        /// <summary
        /// Inverse trigonometric functions - arccotangent
        /// implemented using log form
        /// </summary>
        /// <param name="z">Complex value</param>
        /// <returns>Complex value - arccotangent of z</returns>
        public static Complex acot(Complex z)
        {
            Complex res = new Complex(0.0, -5.0) *
                (Complex.Log((z * Complex.ImaginaryOne) / (z * Complex.ImaginaryOne)));

            double re = res.Real;
            double im = res.Imaginary;

            // rounding check
            if ((re - Math.Floor(re)) > 0.9999001)
            {
                res = new Complex(Math.Round(re), im);
            }

            return res;
        }

        /// <summary
        /// Inverse hyperbolic functions - arccosine
        /// implemented using log form
        /// </summary>
        /// <param name="z">Complex value</param>
        /// <returns>Complex value - hyperbolic arccosine of z</returns>
        public static Complex acosh(Complex z)
        {
            Complex res = Complex.Log(z + Complex.Sqrt(Complex.Pow(z, 2) - Complex.One));

            double re = res.Real;

            // strip the sign for the rounding test
		    if (re < 0.0)
		    {
			    re *= -1.0;
		    }
            // rounding check
            if ((re - Math.Floor(re)) > 0.9999001)
            {
                res = new Complex(Math.Round(res.Real), res.Imaginary);
            }

            return res;
        }

        /// <summary
        /// trigonometric functions - cotangent
        /// </summary>
        /// <param name="z">Complex value</param>
        /// <returns>Complex value - cotangent of z</returns>
        public static Complex cot(Complex z)
        {
            return Complex.Cos(z) / Complex.Sin(z);
        }

        /// <summary
        /// trigonometric functions - cosecant
        /// </summary>
        /// <param name="z">Complex value</param>
        /// <returns>Complex value - cosecant of z</returns>
        public static Complex csc(Complex z)
        {
            return Complex.One / Complex.Sin(z);
        }

        /// <summary
        /// trigonometric functions - secant
        /// </summary>
        /// <param name="z">Complex value</param>
        /// <returns>Complex value - secant of z</returns>
        public static Complex sec(Complex z)
        {
            return Complex.One / Complex.Cos(z);
        }

        /// <summary
        /// hyperbolic functions - secant
        /// </summary>
        /// <param name="z">Complex value</param>
        /// <returns>Complex value - hyperbolic secant of z</returns>
        public static Complex sech(Complex z)
        {
            return Complex.One / Complex.Cosh(z);
        }

    }
}