# Math.Log Method (Double)

.NET Framework (current version)

Returns the natural (base e) logarithm of a specified number.

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

## Syntax

```public static double Log(
double d
)
```

#### Parameters

d
Type: System.Double

The number whose logarithm is to be found.

#### Return Value

Type: System.Double

One of the values in the following table.

d parameter

Return value

Positive

The natural logarithm of d; that is, ln d, or log ed

Zero

NegativeInfinity

Negative

NaN

Equal to NaN

NaN

Equal to PositiveInfinity

PositiveInfinity

## Remarks

Parameter d is specified as a base 10 number.

## Examples

The following example illustrates the Log method.

```using System;
public class Example
{
public static void Main()
{
Console.WriteLine("  Evaluate this identity with selected values for X:");
Console.WriteLine("                              ln(x) = 1 / log[X](B)");
Console.WriteLine();

double[] XArgs = { 1.2, 4.9, 9.9, 0.1 };

foreach (double argX in XArgs)
{
// Find natural log of argX.
Console.WriteLine("                      Math.Log({0}) = {1:E16}",
argX, Math.Log(argX));

// Evaluate 1 / log[X](e).
Console.WriteLine("             1.0 / Math.Log(e, {0}) = {1:E16}",
argX, 1.0 / Math.Log(Math.E, argX));
Console.WriteLine();
}
}
}
// This example displays the following output:
//         Evaluate this identity with selected values for X:
//                                     ln(x) = 1 / log[X](B)
//
//                             Math.Log(1.2) = 1.8232155679395459E-001
//                    1.0 / Math.Log(e, 1.2) = 1.8232155679395459E-001
//
//                             Math.Log(4.9) = 1.5892352051165810E+000
//                    1.0 / Math.Log(e, 4.9) = 1.5892352051165810E+000
//
//                             Math.Log(9.9) = 2.2925347571405443E+000
//                    1.0 / Math.Log(e, 9.9) = 2.2925347571405443E+000
//
//                             Math.Log(0.1) = -2.3025850929940455E+000
//                    1.0 / Math.Log(e, 0.1) = -2.3025850929940455E+000
```

## Version Information

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1