# BigInteger.Log Method (BigInteger)

.NET Framework 4.5

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

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

## Syntax

```'Declaration
Public Shared Function Log ( _
value As BigInteger _
) As Double
```

#### Parameters

value
Type: System.Numerics.BigInteger

The number whose logarithm is to be found.

#### Return Value

Type: System.Double
The natural (base e) logarithm of value, as shown in the table in the Remarks section.

## Exceptions

ExceptionCondition
ArgumentOutOfRangeException

The natural log of value is out of range of the Double data type.

## Remarks

The value parameter is specified as a base 10 number.

The precise return value of this method depends on the sign of value, as the following table shows.

Sign of value parameter

Return value

Positive

The natural logarithm of value; that is, ln value, or log e value.

Zero

Negative

NaN.

To calculate the base 10 logarithm of a BigInteger value, call the Log10 method. To calculate the logarithm of a number in another base, call the Log(BigInteger, Double) method.

You can find the square root of a number by calling the Log method along with the Math.Exp method. Note that the result is Double.PositiveInfinity if the result is greater than Double.MaxValue. The following example calculates the square root of each element in an array of BigInteger values.

```Imports System.Numerics

Module Example
Public Sub Main()
Dim values() As BigInteger = { 2, 100, BigInteger.Pow(1000, 100),
BigInteger.Pow(2, 64) }
For Each value In values
Console.WriteLine("The square root of {0} is {1}", value,
Math.Exp(BigInteger.Log(value) / 2))
Next
End Sub
End Module
' The example displays the following output:
'    The square root of 2 is 1.41421356237309
'    The square root of 100 is 10
'    The square root of 1000000000000000000000000000000000000000000000000000000000000
'    00000000000000000000000000000000000000000000000000000000000000000000000000000000
'    00000000000000000000000000000000000000000000000000000000000000000000000000000000
'    00000000000000000000000000000000000000000000000000000000000000000000000000000000
'     is 9.99999999999988E+149
'    The square root of 18446744073709551616 is 4294967296
```

This method corresponds to the Math.Log(Double) method for the primitive numeric types.

## Version Information

#### .NET Framework

Supported in: 4.6, 4.5, 4

Supported in: 4

#### Portable Class Library

Supported in: Portable Class Library

#### .NET for Windows Store apps

Supported in: Windows 8
Supported in: Windows Phone 8.1

## Platforms

Windows Phone 8.1, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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