Was this page helpful?
Your feedback about this content is important. Let us know what you think.
Additional feedback?
1500 characters remaining
Export (0) Print
Expand All

Complex.Acos Method

Returns the angle that is the arc cosine of the specified complex number.

Namespace:  System.Numerics
Assemblies:   System.Runtime.Numerics (in System.Runtime.Numerics.dll)
  System.Numerics (in System.Numerics.dll)

public static Complex Acos(
	Complex value


Type: System.Numerics.Complex

A complex number that represents a cosine.

Return Value

Type: System.Numerics.Complex
The angle, measured in radians, which is the arc cosine of value.

The Acos method for complex numbers corresponds to the Math.Acos method for real numbers.

The Acos method uses the following formula:

(-ImaginaryOne) * Log(value + ImaginaryOne * Sqrt(One - value * value)))

The following example illustrates the Acos method. It shows that passing the value returned by the Acos method to the Cos method returns the original Complex value.

using System;
using System.Numerics;

public class Example
   public static void Main()
      Complex[] values = { new Complex(.5, 2), 
                           new Complex(.5, -2),
                           new Complex(-.5, 2),
                           new Complex(-.3, -.8) };
      foreach (Complex value in values)
         Console.WriteLine("Cos(ACos({0})) = {1}", value, 
// The example displays the following output: 
//       Cos(ACos((0.5, 2))) = (0.5, 2) 
//       Cos(ACos((0.5, -2))) = (0.5, -2) 
//       Cos(ACos((-0.5, 2))) = (-0.5, 2) 
//       Cos(ACos((-0.3, -0.8))) = (-0.3, -0.8)

.NET Framework

Supported in: 4.6, 4.5, 4

.NET Framework Client Profile

Supported in: 4

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1
© 2015 Microsoft