Math.Log10 メソッド

2008-03-28

指定した数の底 10 の対数を返します。

Public Shared Function Log10( _
   ByVal d As Double _) As Double
[C#]
public static double Log10(doubled);
[C++]
public: static double Log10(doubled);
[JScript]
public static function Log10(
   d : double) : double;

パラメータ

d
対数を検索する対象の数値。

戻り値

d の符号	戻り値
正	d の底 10 の log。つまり、log₁₀ d 。
0	NegativeInfinity
負	NaN

d が NaN に等しい場合、このメソッドは NaN を返します。 d が PositiveInfinity に等しい場合、このメソッドは PositiveInfinity を返します。

解説

パラメータ d は、底 10 で指定されます。

使用例

[Visual Basic, C#, C++] 次に示すのは、 Log10 を使用して、選択した値から対数恒等式を求める例です。

 
' Example for the Math.Log( Double, Double )and Math.Log10( Double ) methods.
Imports System
Imports Microsoft.VisualBasic

Module LogDDLog10
       
    Sub Main()
        Console.WriteLine( _
            "This example of Math.Log( Double, Double ) " + _
            "and Math.Log10( Double )" & vbCrLf & _
            "generates the following output." & vbCrLf)
        Console.WriteLine( _
            "Evaluate these identities with " & _
            "selected values for X and B (base):")
        Console.WriteLine("   log(B)[X] = 1 / log(X)[B]")
        Console.WriteLine("   log(B)[X] = log(10)[X] / log(10)[B]")
        Console.WriteLine("   log(B)[X] = log(B)[10] * log(10)[X]")
          
        UseBaseAndArg(0.1, 1.2)
        UseBaseAndArg(1.2, 4.9)
        UseBaseAndArg(4.9, 9.9)
        UseBaseAndArg(9.9, 0.1)
    End Sub 'Main
       
    ' Evaluate logarithmic identities that are functions of two arguments.
    Sub UseBaseAndArg(argB As Double, argX As Double)

        ' Evaluate log(B)[X] = 1 / log(X)[B].
        Console.WriteLine( _
            vbCrLf & "                   Math.Log({1}, {0}) = {2:E16}" + _
            vbCrLf & "             1.0 / Math.Log({0}, {1}) = {3:E16}", _
            argB, argX, Math.Log(argX, argB), _
            1.0 / Math.Log(argB, argX))
          
        ' Evaluate log(B)[X] = log(10)[X] / log(10)[B].
        Console.WriteLine( _
            "    Math.Log10({1}) / Math.Log10({0}) = {2:E16}", _
            argB, argX, Math.Log10(argX) / Math.Log10(argB))
          
        ' Evaluate log(B)[X] = log(B)[10] * log(10)[X].
        Console.WriteLine( _
            "Math.Log(10.0, {0}) * Math.Log10({1}) = {2:E16}", _
            argB, argX, Math.Log(10.0, argB) * Math.Log10(argX))

    End Sub 'UseBaseAndArg
End Module 'LogDDLog10

' This example of Math.Log( Double, Double ) and Math.Log10( Double )
' generates the following output.
'
' Evaluate these identities with selected values for X and B (base):
'    log(B)[X] = 1 / log(X)[B]
'    log(B)[X] = log(10)[X] / log(10)[B]
'    log(B)[X] = log(B)[10] * log(10)[X]
' 
'                    Math.Log(1.2, 0.1) = -7.9181246047624818E-002
'              1.0 / Math.Log(0.1, 1.2) = -7.9181246047624818E-002
'     Math.Log10(1.2) / Math.Log10(0.1) = -7.9181246047624818E-002
' Math.Log(10.0, 0.1) * Math.Log10(1.2) = -7.9181246047624831E-002
' 
'                    Math.Log(4.9, 1.2) = 8.7166610085093179E+000
'              1.0 / Math.Log(1.2, 4.9) = 8.7166610085093161E+000
'     Math.Log10(4.9) / Math.Log10(1.2) = 8.7166610085093179E+000
' Math.Log(10.0, 1.2) * Math.Log10(4.9) = 8.7166610085093179E+000
' 
'                    Math.Log(9.9, 4.9) = 1.4425396251981288E+000
'              1.0 / Math.Log(4.9, 9.9) = 1.4425396251981288E+000
'     Math.Log10(9.9) / Math.Log10(4.9) = 1.4425396251981288E+000
' Math.Log(10.0, 4.9) * Math.Log10(9.9) = 1.4425396251981291E+000
' 
'                    Math.Log(0.1, 9.9) = -1.0043839404494075E+000
'              1.0 / Math.Log(9.9, 0.1) = -1.0043839404494075E+000
'     Math.Log10(0.1) / Math.Log10(9.9) = -1.0043839404494077E+000
' Math.Log(10.0, 9.9) * Math.Log10(0.1) = -1.0043839404494077E+000

[C#] 
// Example for the Math.Log( double, double ) and Math.Log10( double ) methods.
using System;

class LogDDLog10 
{
    public static void Main() 
    {
        Console.WriteLine( 
            "This example of Math.Log( double, double ) " +
            "and Math.Log10( double )\n" +
            "generates the following output.\n" );
        Console.WriteLine( 
            "Evaluate these identities with " +
            "selected values for X and B (base):" );
        Console.WriteLine( "   log(B)[X] == 1 / log(X)[B]" );
        Console.WriteLine( "   log(B)[X] == log(10)[X] / log(10)[B]" );
        Console.WriteLine( "   log(B)[X] == log(B)[10] * log(10)[X]" );

        UseBaseAndArg(0.1, 1.2);
        UseBaseAndArg(1.2, 4.9);
        UseBaseAndArg(4.9, 9.9);
        UseBaseAndArg(9.9, 0.1);
    }

    // Evaluate logarithmic identities that are functions of two arguments.
    static void UseBaseAndArg(double argB, double argX)
    {
        // Evaluate log(B)[X] == 1 / log(X)[B].
        Console.WriteLine( 
            "\n                   Math.Log({1}, {0}) == {2:E16}" + 
            "\n             1.0 / Math.Log({0}, {1}) == {3:E16}", 
            argB, argX, Math.Log(argX, argB),
            1.0 / Math.Log(argB, argX) );

        // Evaluate log(B)[X] == log(10)[X] / log(10)[B].
        Console.WriteLine( 
            "    Math.Log10({1}) / Math.Log10({0}) == {2:E16}",
            argB, argX, Math.Log10(argX) / Math.Log10(argB) );

        // Evaluate log(B)[X] == log(B)[10] * log(10)[X].
        Console.WriteLine( 
            "Math.Log(10.0, {0}) * Math.Log10({1}) == {2:E16}", 
            argB, argX, Math.Log(10.0, argB) * Math.Log10(argX) );
    }
}

/*
This example of Math.Log( double, double ) and Math.Log10( double )
generates the following output.

Evaluate these identities with selected values for X and B (base):
   log(B)[X] == 1 / log(X)[B]
   log(B)[X] == log(10)[X] / log(10)[B]
   log(B)[X] == log(B)[10] * log(10)[X]

                   Math.Log(1.2, 0.1) == -7.9181246047624818E-002
             1.0 / Math.Log(0.1, 1.2) == -7.9181246047624818E-002
    Math.Log10(1.2) / Math.Log10(0.1) == -7.9181246047624818E-002
Math.Log(10.0, 0.1) * Math.Log10(1.2) == -7.9181246047624831E-002

                   Math.Log(4.9, 1.2) == 8.7166610085093179E+000
             1.0 / Math.Log(1.2, 4.9) == 8.7166610085093161E+000
    Math.Log10(4.9) / Math.Log10(1.2) == 8.7166610085093179E+000
Math.Log(10.0, 1.2) * Math.Log10(4.9) == 8.7166610085093179E+000

                   Math.Log(9.9, 4.9) == 1.4425396251981288E+000
             1.0 / Math.Log(4.9, 9.9) == 1.4425396251981288E+000
    Math.Log10(9.9) / Math.Log10(4.9) == 1.4425396251981288E+000
Math.Log(10.0, 4.9) * Math.Log10(9.9) == 1.4425396251981291E+000

                   Math.Log(0.1, 9.9) == -1.0043839404494075E+000
             1.0 / Math.Log(9.9, 0.1) == -1.0043839404494075E+000
    Math.Log10(0.1) / Math.Log10(9.9) == -1.0043839404494077E+000
Math.Log(10.0, 9.9) * Math.Log10(0.1) == -1.0043839404494077E+000
*/

[C++] 
// Example for the Math::Log( double, double ) and Math::Log10( double ) methods.
#using <mscorlib.dll>
using namespace System;

// Evaluate logarithmic identities that are functions of two arguments.
void UseBaseAndArg(double argB, double argX)
{
    // Evaluate log(B)[X] == 1 / log(X)[B].
    Console::WriteLine( 
        S"\n                    Math::Log({1}, {0}) == {2:E16}" 
        S"\n              1.0 / Math::Log({0}, {1}) == {3:E16}", 
        __box(argB), __box(argX), 
        __box(Math::Log(argX, argB)),
        __box(1.0 / Math::Log(argB, argX)) );

    // Evaluate log(B)[X] == log(10)[X] / log(10)[B].
    Console::WriteLine( 
        S"    Math::Log10({1}) / Math::Log10({0}) == {2:E16}",
        __box(argB), __box(argX), 
        __box(Math::Log10(argX) / Math::Log10(argB)) );

    // Evaluate log(B)[X] == log(B)[10] * log(10)[X].
    Console::WriteLine( 
        S"Math::Log(10.0, {0}) * Math::Log10({1}) == {2:E16}", 
        __box(argB), __box(argX), 
        __box(Math::Log(10.0, argB) * Math::Log10(argX)) );
}

void main() 
{
    Console::WriteLine( 
        S"This example of Math::Log( double, double ) "
        S"and Math::Log10( double )\n"
        S"generates the following output.\n" );
    Console::WriteLine( 
        S"Evaluate these identities with "
        S"selected values for X and B (base):" );
    Console::WriteLine( S"   log(B)[X] == 1 / log(X)[B]" );
    Console::WriteLine( S"   log(B)[X] == log(10)[X] / log(10)[B]" );
    Console::WriteLine( S"   log(B)[X] == log(B)[10] * log(10)[X]" );

    UseBaseAndArg(0.1, 1.2);
    UseBaseAndArg(1.2, 4.9);
    UseBaseAndArg(4.9, 9.9);
    UseBaseAndArg(9.9, 0.1);
}

/*
This example of Math::Log( double, double ) and Math::Log10( double )
generates the following output.

Evaluate these identities with selected values for X and B (base):
   log(B)[X] == 1 / log(X)[B]
   log(B)[X] == log(10)[X] / log(10)[B]
   log(B)[X] == log(B)[10] * log(10)[X]

                    Math::Log(1.2, 0.1) == -7.9181246047624818E-002
              1.0 / Math::Log(0.1, 1.2) == -7.9181246047624818E-002
    Math::Log10(1.2) / Math::Log10(0.1) == -7.9181246047624818E-002
Math::Log(10.0, 0.1) * Math::Log10(1.2) == -7.9181246047624831E-002

                    Math::Log(4.9, 1.2) == 8.7166610085093179E+000
              1.0 / Math::Log(1.2, 4.9) == 8.7166610085093161E+000
    Math::Log10(4.9) / Math::Log10(1.2) == 8.7166610085093179E+000
Math::Log(10.0, 1.2) * Math::Log10(4.9) == 8.7166610085093179E+000

                    Math::Log(9.9, 4.9) == 1.4425396251981288E+000
              1.0 / Math::Log(4.9, 9.9) == 1.4425396251981288E+000
    Math::Log10(9.9) / Math::Log10(4.9) == 1.4425396251981288E+000
Math::Log(10.0, 4.9) * Math::Log10(9.9) == 1.4425396251981291E+000

                    Math::Log(0.1, 9.9) == -1.0043839404494075E+000
              1.0 / Math::Log(9.9, 0.1) == -1.0043839404494075E+000
    Math::Log10(0.1) / Math::Log10(9.9) == -1.0043839404494077E+000
Math::Log(10.0, 9.9) * Math::Log10(0.1) == -1.0043839404494077E+000
*/

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必要条件

プラットフォーム: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 ファミリ, .NET Compact Framework - Windows CE .NET, Common Language Infrastructure (CLI) Standard

参照

Math クラス | Math メンバ | System 名前空間

次の方法で共有

Math.Log10 メソッド

パラメータ

戻り値

解説

使用例

必要条件

参照

その他のリソース