Log Function |
System.Math
Math.Log( d )
or:
Math.Log( a , newbase )
A numeric expression greater than zero
The base of the logarithm
Double
Returns the natural (base e) logarithm of a given number (the first syntax) or the logarithm of a given number in a specified base (the second syntax)
The natural logarithm is the logarithm base e, a constant whose value is approximately 2.718282. The natural logarithm satisfies the equation:
e^Log(x) = x
In other words, the natural logarithm function is the inverse function of the exponential function.
d or a , the value whose natural logarithm the function is to return, must be a positive real number. If number is negative or zero, the function generates runtime error 5, "Invalid procedure call or argument."
This is a Shared member, so it can be used without creating any objects.
You can calculate base- n logarithms for any number, x , by dividing the natural logarithm of x by the natural logarithm of n , as the following expression illustrates:
Log n ( x ) = Log( x ) / Log( n )
For example, the Log10 function shows the source code for a custom function that calculates base-10 logarithms:
Static Function Log10(X) Log10 = Log(X) / Log(10#) End Function
The inverse trigonometric functions, which are not intrinsic to VB, can be computed using the value returned by the Log function. The functions and their formulas are:
HArcsin(X) = Log(X + Sqr(X * X + 1))
HArccos(X) = Log(X + Sqr(X * X - 1))
HArctan(X) = Log((1 + X) / (1 - X)) / 2
HArcsec(X) = Log((Sqr(-X * X + 1) + 1) / X)
HArccosec(X) = Log((Sgn(X) * Sqr(X * X + 1) +1) / X)
HArccotan(X) = Log((X + 1) / (X - 1)) / 2
Exp Function, Log10 Function