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Math.Exp Method

Returns e raised to the specified power.

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

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

returnValue = Math.Exp(d)

Parameters

d
Type: System.Double

A number specifying a power.

Return Value

Type: System.Double
The number e raised to the power d. If d equals NaN or PositiveInfinity, that value is returned. If d equals NegativeInfinity, 0 is returned.

Use the Pow method to calculate powers of other bases.

Exp is the inverse of Log.

The following example uses Exp to evaluate certain exponential and logarithmic identities for selected values.

' Example for the Math.Exp( Double ) method. 
Imports System
Imports Microsoft.VisualBasic

Module ExpDemo

    Sub Main()
        Console.WriteLine( _
            "This example of Math.Exp( Double ) " & _
            "generates the following output." & vbCrLf)
        Console.WriteLine( _
            "Evaluate [e ^ ln(X) == ln(e ^ X) == X] " & _
            "with selected values for X:")

        UseLnExp(0.1)
        UseLnExp(1.2)
        UseLnExp(4.9)
        UseLnExp(9.9)

        Console.WriteLine( vbCrLf & _
            "Evaluate these identities with selected values for X and Y:")
        Console.WriteLine("   (e ^ X) * (e ^ Y) = e ^ (X + Y)")
        Console.WriteLine("   (e ^ X) ^ Y = e ^ (X * Y)")
        Console.WriteLine("   X ^ Y = e ^ (Y * ln(X))")

        UseTwoArgs(0.1, 1.2)
        UseTwoArgs(1.2, 4.9)
        UseTwoArgs(4.9, 9.9)
    End Sub 'Main

    ' Evaluate logarithmic/exponential identity with a given argument. 
    Sub UseLnExp(arg As Double)

        ' Evaluate e ^ ln(X) = ln(e ^ X) = X.
        Console.WriteLine( _
            vbCrLf & "      Math.Exp(Math.Log({0})) = {1:E16}" + _
            vbCrLf & "      Math.Log(Math.Exp({0})) = {2:E16}", _
            arg, Math.Exp(Math.Log(arg)), Math.Log(Math.Exp(arg)))
    End Sub 'UseLnExp

    ' Evaluate exponential identities that are functions of two arguments. 
    Sub UseTwoArgs(argX As Double, argY As Double)

        ' Evaluate (e ^ X) * (e ^ Y) = e ^ (X + Y).
        Console.WriteLine( _
            vbCrLf & "Math.Exp({0}) * Math.Exp({1}) = {2:E16}" + _
            vbCrLf & "          Math.Exp({0} + {1}) = {3:E16}", _
            argX, argY, Math.Exp(argX) * Math.Exp(argY), _
            Math.Exp((argX + argY)))

        ' Evaluate (e ^ X) ^ Y = e ^ (X * Y).
        Console.WriteLine( _
            " Math.Pow(Math.Exp({0}), {1}) = {2:E16}" + _
            vbCrLf & "          Math.Exp({0} * {1}) = {3:E16}", _
            argX, argY, Math.Pow(Math.Exp(argX), argY), _
            Math.Exp((argX * argY)))

        ' Evaluate X ^ Y = e ^ (Y * ln(X)).
        Console.WriteLine( _
            "           Math.Pow({0}, {1}) = {2:E16}" + _
            vbCrLf & "Math.Exp({1} * Math.Log({0})) = {3:E16}", _
            argX, argY, Math.Pow(argX, argY), _
            Math.Exp((argY * Math.Log(argX))))

    End Sub 'UseTwoArgs
End Module 'ExpDemo

' This example of Math.Exp( Double ) generates the following output. 
'  
' Evaluate [e ^ ln(X) == ln(e ^ X) == X] with selected values for X: 
'  
'       Math.Exp(Math.Log(0.1)) = 1.0000000000000001E-001 
'       Math.Log(Math.Exp(0.1)) = 1.0000000000000008E-001 
'  
'       Math.Exp(Math.Log(1.2)) = 1.2000000000000000E+000 
'       Math.Log(Math.Exp(1.2)) = 1.2000000000000000E+000 
'  
'       Math.Exp(Math.Log(4.9)) = 4.9000000000000012E+000 
'       Math.Log(Math.Exp(4.9)) = 4.9000000000000004E+000 
'  
'       Math.Exp(Math.Log(9.9)) = 9.9000000000000004E+000 
'       Math.Log(Math.Exp(9.9)) = 9.9000000000000004E+000 
'  
' Evaluate these identities with selected values for X and Y: 
'    (e ^ X) * (e ^ Y) = e ^ (X + Y) 
'    (e ^ X) ^ Y = e ^ (X * Y) 
'    X ^ Y = e ^ (Y * ln(X)) 
'  
' Math.Exp(0.1) * Math.Exp(1.2) = 3.6692966676192444E+000 
'           Math.Exp(0.1 + 1.2) = 3.6692966676192444E+000 
'  Math.Pow(Math.Exp(0.1), 1.2) = 1.1274968515793757E+000 
'           Math.Exp(0.1 * 1.2) = 1.1274968515793757E+000 
'            Math.Pow(0.1, 1.2) = 6.3095734448019331E-002 
' Math.Exp(1.2 * Math.Log(0.1)) = 6.3095734448019344E-002 
'  
' Math.Exp(1.2) * Math.Exp(4.9) = 4.4585777008251705E+002 
'           Math.Exp(1.2 + 4.9) = 4.4585777008251716E+002 
'  Math.Pow(Math.Exp(1.2), 4.9) = 3.5780924170885260E+002 
'           Math.Exp(1.2 * 4.9) = 3.5780924170885277E+002 
'            Math.Pow(1.2, 4.9) = 2.4433636334442981E+000 
' Math.Exp(4.9 * Math.Log(1.2)) = 2.4433636334442981E+000 
'  
' Math.Exp(4.9) * Math.Exp(9.9) = 2.6764450551890982E+006 
'           Math.Exp(4.9 + 9.9) = 2.6764450551891015E+006 
'  Math.Pow(Math.Exp(4.9), 9.9) = 1.1684908531676833E+021 
'           Math.Exp(4.9 * 9.9) = 1.1684908531676829E+021 
'            Math.Pow(4.9, 9.9) = 6.8067718210957060E+006 
' Math.Exp(9.9 * Math.Log(4.9)) = 6.8067718210956985E+006

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

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

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

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