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C Math log() Function

❮ Math Functions


Example

Return the natural logarithm of different numbers:

const double E = 2.718281828;
printf("%f", log(6.0));
printf("%f", log(E));
printf("%f", log(2.0));
printf("%f", log(1.0));
printf("%f", log(0.0));
printf("%f", log(-1.0));
Try it Yourself »

Definition and Usage

The log() function returns the natural logarithm of a number.

The log() function is defined in the <math.h> header file.

The natural logarithm is the logarithm with base e. The value of e is approximately 2.718282. Some implementations of the <math.h> library include a constant M_E but it is not guaranteed to be available.


Syntax

One of the following:

log(double number);

Parameter Values

Parameter Description
number Required. Specifies the value to calculate the logarithm for.
If the value is negative, it returns NaN (Not a Number).
If the value is 0, it returns -infinity.

Technical Details

Returns: A double value representing the natural logarithm of a number.

❮ Math Functions


Related Pages

C Functions Tutorial

C Math Functions Tutorial


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