expm1, expm1f, expm1l - compute exponential function

Syntax	#include <math.h> double expm1(double x); C11 float expm1f(float x); long double expm1l(long double x); (End)
Description	These functions compute ex-1.0.
Return val.	e x -1.0	if successful.
	HUGE_VAL HUGE_VALF HUGE_VALL	depending on the function type, if an overflow occurs. errno is set to indicate the error.
Errors	expm1(), expm1f() and expm1l() will fail if
	ERANGE	Overflow; the return value is too high.
Notes	For small x values, the result of expm1(x) can be more accurate than the value of exp(x)-1.0. The functions expm1() and log1p() are helpful for computing the expression ((1+x) n -1)/x, in the format: expm1(n*log1p(x))/x in the case of very small values of x. This function can also be used to precisely represent inverse hyperbolic functions.
See also	exp(), ilogb(), log1p(), math.h.