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# Manual Reference Pages  -  LOG10F (3)

### NAME

log, logf, logl, log10, log10f, log10l, log2, log2f, log2l, log1p, log1pf, log1pl - logarithm functions

Library
Synopsis
Description
Return Values
Standards

.Lb libm

### SYNOPSIS

.In math.h double log double x float logf float x long double logl long double x double log10 double x float log10f float x long double log10l long double x double log2 double x float log2f float x long double log2l long double x double log1p double x float log1pf float x long double log1pl long double x

### DESCRIPTION

The log, logf, and logl functions compute the natural logarithm of x.

The log10, log10f, and log10l functions compute the logarithm base 10 of x, while log2, log2f, and log2l compute the logarithm base 2 of x.

The log1p, log1pf, and log1pl functions compute the natural logarithm of 1 + x. Computing the natural logarithm as log1p(x) is more accurate than computing it as log(1 + x) when x is close to zero.

### RETURN VALUES

These functions return the requested logarithm; the logarithm of 1 is +0. An attempt to take the logarithm of ±0 results in a divide-by-zero exception, and -oo is returned. Otherwise, attempting to take the logarithm of a negative number results in an invalid exception and a return value of NaN.

exp(3), ilogb(3), math(3), pow(3)

### STANDARDS

The log, logf, logl, log10, log10f, log10l, log2, log2f, log2l, log1p, log1pf, and log1pl functions conform to -isoC-99.
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