`expm1`

, `expm1f`

---exponential minus 1#include <math.h> double expm1(doublex); float expm1f(floatx);

**Description**

`expm1`

and `expm1f`

calculate the exponential of `x`
and subtract 1, that is,
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(`

would lose many
significant digits.
`x`)-1

**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).

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