# Math.Exp Method

.NET Framework 2.0

Returns e raised to the specified power.

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

## Syntax

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

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

#### Parameters

d

A number specifying a power.

#### Return Value

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.

## Remarks

Use the Pow method to calculate powers of other bases.

Exp is the inverse of Log.

## Example

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

```
```// Example for the Math.Exp( double ) method.
import System.*;

class ExpDemo
{
public static void main(String[] args)
{
Console.WriteLine(("This example of Math.Exp( double ) "
+ "generates the following output.\n"));
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(("\nEvaluate 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);
} //main

// Evaluate logarithmic/exponential identity with a given argument.
static void UseLnExp(double arg)
{
// Evaluate e ^ ln(X) == ln(e ^ X) == X.
Console.WriteLine("\n     Math.Exp(Math.Log({0})) == {1}\n"
+ "     Math.Log(Math.Exp({0})) == {2}",
System.Convert.ToString(arg),
((System.Double)System.Math.Exp(
System.Math.Log(arg))).ToString("E16"),
((System.Double)System.Math.Log(
System.Math.Exp(arg))).ToString("E16"));
} //UseLnExp

// Evaluate exponential identities that are functions of two arguments.
static void UseTwoArgs(double argX, double argY)
{
// Evaluate (e ^ X) * (e ^ Y) == e ^ (X + Y).
Console.WriteLine("\nMath.Exp({0}) * Math.Exp({1}) == {2}"
+ "\n          Math.Exp({0} + {1}) == {3}",
new Object[] {System.Convert.ToString(argX),
System.Convert.ToString(argY),((System.Double )
(System.Math.Exp(argX) * System.Math.Exp(argY))).ToString("E16"),
((System.Double )System.Math.Exp((argX + argY))).ToString("E16")});

// Evaluate (e ^ X) ^ Y == e ^ (X * Y).
Console.WriteLine(" Math.Pow(Math.Exp({0}), {1}) == {2}"
+ "\n          Math.Exp({0} * {1}) == {3}",
new Object[] { System.Convert.ToString(argX),
System.Convert.ToString(argY),((System.Double)System.Math.Pow
(System.Math.Exp(argX),argY)).ToString("E16"),
((System.Double)System.Math.Exp((argX * argY))).ToString("E16")});

// Evaluate X ^ Y == e ^ (Y * ln(X)).
Console.WriteLine("           Math.Pow({0}, {1}) == {2}"
+ "\nMath.Exp({1} * Math.Log({0})) == {3}",
new Object[] { System.Convert.ToString(argX),
System.Convert.ToString(argY),
((System.Double)System.Math.Pow(argX, argY)).ToString("E16"),
((System.Double)System.Math.Exp(
(argY * System.Math.Log(argX)))).ToString("E16") });
} //UseTwoArgs
} //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
*/

```

## Platforms

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.

## Version Information

#### .NET Framework

Supported in: 2.0, 1.1, 1.0

#### .NET Compact Framework

Supported in: 2.0, 1.0

Math Class
Math Members
System Namespace
E
Pow
Log