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Math.Acos Method

Returns the angle whose cosine is the specified number.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)

[SecuritySafeCriticalAttribute]
public static double Acos(
	double d
)

Parameters

d
Type: System.Double
A number representing a cosine, where d must be greater than or equal to -1, but less than or equal to 1.

Return Value

Type: System.Double
An angle, θ, measured in radians, such that 0 θ π
-or-
NaN if d < -1 or d > 1 or d equals NaN.

Multiply the return value by 180/Math.PI to convert from radians to degrees.

The following code sample uses Acos to assist in the computation of the inner angles of a given trapezoid.


/// <summary>
/// The following class represents simple functionality of the trapezoid.
/// </summary>
class Example
{
   private double m_longBase;
   private double m_shortBase;
   private double m_leftLeg;
   private double m_rightLeg;

   public Example(double longbase, double shortbase, double leftLeg, double rightLeg)
   {
      m_longBase = Math.Abs(longbase);
      m_shortBase = Math.Abs(shortbase);
      m_leftLeg = Math.Abs(leftLeg);
      m_rightLeg = Math.Abs(rightLeg);
   }

   private double GetRightSmallBase()
   {
      return (Math.Pow(m_rightLeg, 2.0) - Math.Pow(m_leftLeg, 2.0) + Math.Pow(m_longBase, 2.0) + Math.Pow(m_shortBase, 2.0) - 2 * m_shortBase * m_longBase) / (2 * (m_longBase - m_shortBase));
   }

   public double GetHeight()
   {
      double x = GetRightSmallBase();
      return Math.Sqrt(Math.Pow(m_rightLeg, 2.0) - Math.Pow(x, 2.0));
   }

   public double GetSquare()
   {
      return GetHeight() * m_longBase / 2.0;
   }

   public double GetLeftBaseRadianAngle()
   {
      double sinX = GetHeight() / m_leftLeg;
      return Math.Round(Math.Asin(sinX), 2);
   }

   public double GetRightBaseRadianAngle()
   {
      double x = GetRightSmallBase();
      double cosX = (Math.Pow(m_rightLeg, 2.0) + Math.Pow(x, 2.0) - Math.Pow(GetHeight(), 2.0)) / (2 * x * m_rightLeg);
      return Math.Round(Math.Acos(cosX), 2);
   }

   public double GetLeftBaseDegreeAngle()
   {
      double x = GetLeftBaseRadianAngle() * 180 / Math.PI;
      return Math.Round(x, 2);
   }

   public double GetRightBaseDegreeAngle()
   {
      double x = GetRightBaseRadianAngle() * 180 / Math.PI;
      return Math.Round(x, 2);
   }

   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      Example trpz = new Example(20.0, 10.0, 8.0, 6.0);
      outputBlock.Text += String.Format("The trapezoid's bases are 20.0 and 10.0, the trapezoid's legs are 8.0 and 6.0") + "\n";
      double h = trpz.GetHeight();
      outputBlock.Text += "Trapezoid height is: " + h.ToString() + "\n";
      double dxR = trpz.GetLeftBaseRadianAngle();
      outputBlock.Text += "Trapezoid left base angle is: " + dxR.ToString() + " Radians" + "\n";
      double dyR = trpz.GetRightBaseRadianAngle();
      outputBlock.Text += "Trapezoid right base angle is: " + dyR.ToString() + " Radians" + "\n";
      double dxD = trpz.GetLeftBaseDegreeAngle();
      outputBlock.Text += "Trapezoid left base angle is: " + dxD.ToString() + " Degrees" + "\n";
      double dyD = trpz.GetRightBaseDegreeAngle();
      outputBlock.Text += "Trapezoid left base angle is: " + dyD.ToString() + " Degrees" + "\n";
   }
}


Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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