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Math.Acos Method

Returns the angle whose cosine is the specified number.

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

'Declaration
Public Shared Function Acos ( _
	d As Double _
) As Double
'Usage
Dim d As Double
Dim returnValue As Double

returnValue = Math.Acos(d)
public static double Acos (
	double d
)
public static function Acos (
	d : double
) : double

Parameters

d

A number representing a cosine, where -1 d 1.

Return Value

An angle, θ, measured in radians, such that 0 θπ -or- NaN if d < -1 or d > 1.

Multiply the return value by 180/π 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.

'The following class represents simple functionallity 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 trpezoid'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 left base angle is: " + dyD.ToString() + " Degrees")
    End Sub

End Class


/// <summary>
/// The following class represents simple functionallity of the Trapezoid
/// </summary>
class MathTrapezoidSample
{
    private double mLongBase;
    private double mShortBase;
    private double mLeftLeg;
    private double mRightLeg;
    public MathTrapezoidSample(double longBase, double shortBase, 
        double leftLeg, double rightLeg)
    {
        mLongBase = System.Math.Abs(longBase);
        mShortBase = System.Math.Abs(shortBase);
        mLeftLeg = System.Math.Abs(leftLeg);
        mRightLeg = System.Math.Abs(rightLeg);
    } //MathTrapezoidSample

    private double GetRightSmallBase()
    {
        return (System.Math.Pow(mRightLeg, 2.0) 
            - System.Math.Pow(mLeftLeg, 2.0) 
            + System.Math.Pow(mLongBase, 2.0) 
            + System.Math.Pow(mShortBase, 2.0) 
            - 2 * mShortBase * mLongBase) / (2 * (mLongBase - mShortBase));
    } //GetRightSmallBase

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

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

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

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

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

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

    public static void main(String[] args)
    {
        MathTrapezoidSample trpz = 
            new MathTrapezoidSample(20.0, 10.0, 8.0, 6.0);
        Console.WriteLine("The trpezoid'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: " 
            + System.Convert.ToString(h));
        double dxR = trpz.GetLeftBaseRadianAngle();
        Console.WriteLine("Trapezoid left base angle is: " 
            + System.Convert.ToString(dxR) + " Radians");
        double dyR = trpz.GetRightBaseRadianAngle();
        Console.WriteLine("Trapezoid right base angle is: " 
            + System.Convert.ToString(dyR) + " Radians");
        double dxD = trpz.GetLeftBaseDegreeAngle();
        Console.WriteLine("Trapezoid left base angle is: " 
            + System.Convert.ToString(dxD) + " Degrees");
        double dyD = trpz.GetRightBaseDegreeAngle();
        Console.WriteLine("Trapezoid left base angle is: " 
            + System.Convert.ToString(dyD) + " Degrees");
    } //main
} //MathTrapezoidSample

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

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