C Math log() Function
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 |
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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. |
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