float atanhf( float arg );
(1) (since C99)double atanh( double arg );
(2) (since C99)long double atanhl( long double arg );
(3) (since C99)#define atanh( arg )
(4) (since C99)1-3) Computes the inverse hyperbolic tangent of arg.
4)Type-generic macro: If the argument has type
long double,
atanhl
is called. Otherwise, if the argument has integer type or the type
double,
atanh
is called. Otherwise,
atanhf
is called. If the argument is complex, then the macro invokes the corresponding complex function (
catanhf,
catanh,
catanhl).
[edit] Parameters arg - floating_point value representing the area of a hyperbolic sector [edit] Return valueIf no errors occur, the inverse hyperbolic tangent of arg (tanh-1
(arg), or artanh(arg)), is returned.
If a domain error occurs, an implementation-defined value is returned (NaN where supported).
If a pole error occurs, ±HUGE_VAL, ±HUGE_VALF, or ±HUGE_VALL is returned (with the correct sign).
If a range error occurs due to underflow, the correct result (after rounding) is returned.
[edit] Error handlingErrors are reported as specified in math_errhandling.
If the argument is not on the interval [-1, +1], a range error occurs.
If the argument is ±1, a pole error occurs.
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
Although the C standard names this function "arc hyperbolic tangent", the inverse functions of the hyperbolic functions are the area functions. Their argument is the area of a hyperbolic sector, not an arc. The correct name is "inverse hyperbolic tangent" (used by POSIX) or "area hyperbolic tangent".
POSIX specifies that in case of underflow, arg is returned unmodified, and if that is not supported, an implementation-defined value no greater than DBL_MIN, FLT_MIN, and LDBL_MIN is returned.
[edit] Example#include <errno.h>
#include <fenv.h>
#include <float.h>
#include <math.h>
#include <stdio.h>
// #pragma STDC FENV_ACCESS ON
int main(void)
{
printf("atanh(0) = %f\natanh(-0) = %f\n", atanh(0), atanh(-0.0));
printf("atanh(0.9) = %f\n", atanh(0.9));
// error handling
errno = 0; feclearexcept(FE_ALL_EXCEPT);
printf("atanh(-1) = %f\n", atanh(-1));
if (errno == ERANGE)
perror(" errno == ERANGE");
if (fetestexcept(FE_DIVBYZERO))
puts(" FE_DIVBYZERO raised");
}
Possible output:
atanh(0) = 0.000000
atanh(-0) = -0.000000
atanh(0.9) = 1.472219
atanh(-1) = -inf
errno == ERANGE: Numerical result out of range
FE_DIVBYZERO raised[edit] References
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