# libm.info: expm1

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# `expm1', `expm1f'--exponential minus 1

*Synopsis*
#include <math.h>
double expm1(double X);
float expm1f(float X);
*Description*
`expm1' and `expm1f' calculate the exponential of X and subtract 1,
that is, e raised to the power X minus 1 (where e is the base of the
natural system of logarithms, approximately 2.71828). The result is
accurate even for small values of X, where using `exp(X)-1' would lose
many significant digits.

*Returns*
e raised to the power X, minus 1.

*Portability*
Neither `expm1' nor `expm1f' is required by ANSI C or by the System V
Interface Definition (Issue 2).

Created Mon Nov 8 17:42:56 2004 on tillpc with info_to_html version 0.9.6.