Math.Acos(Double) Method

public:
 static double Acos(double d);

public static double Acos(double d);

static member Acos : double -> double

Public Shared Function Acos (d As Double) As Double

Parameters

Returns

An angle, θ, measured in radians, such that 0 ≤ θ ≤ π.

-or-

NaN if d < -1 or d > 1 or d equals NaN.

Examples

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

/// <summary>
/// The following class represents simple functionality of the trapezoid.
/// </summary>
using System;

namespace MathClassCS
{
 class MathTrapezoidSample
 {
 private double m_longBase;
 private double m_shortBase;
 private double m_leftLeg;
 private double m_rightLeg;

 public MathTrapezoidSample(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);
 }

 static void Main(string[] args)
 {
 MathTrapezoidSample trpz = new MathTrapezoidSample(20.0, 10.0, 8.0, 6.0);
 Console.WriteLine("The trapezoid's bases are 20.0 and 10.0, the trapezoid's legs are 8.0 and 6.0");
 double h = trpz.GetHeight();
 Console.WriteLine("Trapezoid height is: " + h.ToString());
 double dxR = trpz.GetLeftBaseRadianAngle();
 Console.WriteLine("Trapezoid left base angle is: " + dxR.ToString() + " Radians");
 double dyR = trpz.GetRightBaseRadianAngle();
 Console.WriteLine("Trapezoid right base angle is: " + dyR.ToString() + " Radians");
 double dxD = trpz.GetLeftBaseDegreeAngle();
 Console.WriteLine("Trapezoid left base angle is: " + dxD.ToString() + " Degrees");
 double dyD = trpz.GetRightBaseDegreeAngle();
 Console.WriteLine("Trapezoid right base angle is: " + dyD.ToString() + " Degrees");
 }
 }
}

open System

/// The following class represents simple functionality of the trapezoid.
type MathTrapezoidSample(longbase, shortbase, leftLeg, rightLeg) =
 member _.GetRightSmallBase() =
 (Math.Pow(rightLeg, 2.) - Math.Pow(leftLeg, 2.) + Math.Pow(longbase, 2.) + Math.Pow(shortbase, 2.) - 2. * shortbase * longbase) / (2. * (longbase - shortbase))

 member this.GetHeight() =
 let x = this.GetRightSmallBase()
 Math.Sqrt(Math.Pow(rightLeg, 2.) - Math.Pow(x, 2.))

 member this.GetSquare() =
 this.GetHeight() * longbase / 2.

 member this.GetLeftBaseRadianAngle() =
 let sinX = this.GetHeight() / leftLeg
 Math.Round(Math.Asin sinX,2)

 member this.GetRightBaseRadianAngle() =
 let x = this.GetRightSmallBase()
 let cosX = (Math.Pow(rightLeg, 2.) + Math.Pow(x, 2.) - Math.Pow(this.GetHeight(), 2.))/(2. * x * rightLeg)
 Math.Round(Math.Acos cosX, 2)

 member this.GetLeftBaseDegreeAngle() =
 let x = this.GetLeftBaseRadianAngle() * 180. / Math.PI
 Math.Round(x, 2)

 member this.GetRightBaseDegreeAngle() =
 let x = this.GetRightBaseRadianAngle() * 180. / Math.PI
 Math.Round(x, 2)

let trpz = MathTrapezoidSample(20., 10., 8., 6.)
printfn "The trapezoid's bases are 20.0 and 10.0, the trapezoid's legs are 8.0 and 6.0"
let h = trpz.GetHeight()
printfn $"Trapezoid height is: {h}"
let dxR = trpz.GetLeftBaseRadianAngle()
printfn $"Trapezoid left base angle is: {dxR} Radians"
let dyR = trpz.GetRightBaseRadianAngle()
printfn $"Trapezoid right base angle is: {dyR} Radians"
let dxD = trpz.GetLeftBaseDegreeAngle()
printfn $"Trapezoid left base angle is: {dxD} Degrees"
let dyD = trpz.GetRightBaseDegreeAngle()
printfn $"Trapezoid right base angle is: {dyD} Degrees"

'The following class represents simple functionality of the trapezoid.
Class MathTrapezoidSample

 Private m_longBase As Double
 Private m_shortBase As Double
 Private m_leftLeg As Double
 Private m_rightLeg As Double

 Public Sub New(ByVal longbase As Double, ByVal shortbase As Double, ByVal leftLeg As Double, ByVal rightLeg As Double)
 m_longBase = Math.Abs(longbase)
 m_shortBase = Math.Abs(shortbase)
 m_leftLeg = Math.Abs(leftLeg)
 m_rightLeg = Math.Abs(rightLeg)
 End Sub

 Private Function GetRightSmallBase() As Double
 GetRightSmallBase = (Math.Pow(m_rightLeg, 2) - Math.Pow(m_leftLeg, 2) + Math.Pow(m_longBase, 2) + Math.Pow(m_shortBase, 2) - 2 * m_shortBase * m_longBase) / (2 * (m_longBase - m_shortBase))
 End Function

 Public Function GetHeight() As Double
 Dim x As Double = GetRightSmallBase()
 GetHeight = Math.Sqrt(Math.Pow(m_rightLeg, 2) - Math.Pow(x, 2))
 End Function

 Public Function GetSquare() As Double
 GetSquare = GetHeight() * m_longBase / 2
 End Function

 Public Function GetLeftBaseRadianAngle() As Double
 Dim sinX As Double = GetHeight() / m_leftLeg
 GetLeftBaseRadianAngle = Math.Round(Math.Asin(sinX), 2)
 End Function

 Public Function GetRightBaseRadianAngle() As Double
 Dim x As Double = GetRightSmallBase()
 Dim cosX As Double = (Math.Pow(m_rightLeg, 2) + Math.Pow(x, 2) - Math.Pow(GetHeight(), 2)) / (2 * x * m_rightLeg)
 GetRightBaseRadianAngle = Math.Round(Math.Acos(cosX), 2)
 End Function

 Public Function GetLeftBaseDegreeAngle() As Double
 Dim x As Double = GetLeftBaseRadianAngle() * 180 / Math.PI
 GetLeftBaseDegreeAngle = Math.Round(x, 2)
 End Function

 Public Function GetRightBaseDegreeAngle() As Double
 Dim x As Double = GetRightBaseRadianAngle() * 180 / Math.PI
 GetRightBaseDegreeAngle = Math.Round(x, 2)
 End Function

 Public Shared Sub Main()
 Dim trpz As MathTrapezoidSample = New MathTrapezoidSample(20, 10, 8, 6)
 Console.WriteLine("The trapezoid's bases are 20.0 and 10.0, the trapezoid's legs are 8.0 and 6.0")
 Dim h As Double = trpz.GetHeight()
 Console.WriteLine("Trapezoid height is: " + h.ToString())
 Dim dxR As Double = trpz.GetLeftBaseRadianAngle()
 Console.WriteLine("Trapezoid left base angle is: " + dxR.ToString() + " Radians")
 Dim dyR As Double = trpz.GetRightBaseRadianAngle()
 Console.WriteLine("Trapezoid right base angle is: " + dyR.ToString() + " Radians")
 Dim dxD As Double = trpz.GetLeftBaseDegreeAngle()
 Console.WriteLine("Trapezoid left base angle is: " + dxD.ToString() + " Degrees")
 Dim dyD As Double = trpz.GetRightBaseDegreeAngle()
 Console.WriteLine("Trapezoid right base angle is: " + dyD.ToString() + " Degrees")
 End Sub
End Class

Remarks

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

This method calls into the underlying C runtime, and the exact result or valid input range may differ between different operating systems or architectures.