Math.Log Method (Double)
.NET Framework (current version)
Returns the natural (base e) logarithm of a specified number.
Assembly: mscorlib (in mscorlib.dll)
Parameters
- d
-
Type:
System.Double
The number whose logarithm is to be found.
Return Value
Type: System.DoubleOne 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 | |
Negative | |
Equal to NaN | |
Equal to PositiveInfinity |
Parameter d is specified as a base 10 number.
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
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
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
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