Math.Cosh returns the hyperbolic cosine
using System; class SinhCosh { public static void Main() { UseSinhCosh(4.9); } static void UseSinhCosh(double arg) { double sinhArg = Math.Sinh(arg); double coshArg = Math.Cosh(arg); Console.WriteLine(Math.Sinh(arg)); Console.WriteLine(Math.Cosh(arg) ); } }