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

Math.Exp Method

Returns e raised to the specified power.

Namespace:  System
Assemblies:   mscorlib (in mscorlib.dll)
  System.Runtime.Extensions (in System.Runtime.Extensions.dll)

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

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.

e is a mathematical constant whose value is approximately 2.71828.

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

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0, 2.0, 1.0

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8
Show:
© 2015 Microsoft