acosh, acoshf, acoshl

Parameters

Return value

If no errors occur, the inverse hyperbolic cosine of arg ( cosh -1 (arg) , or arcosh(arg) ) on the interval [0, +∞] , is returned.

If a domain error occurs, an implementation-defined value is returned (NaN where supported).

Error handling

Errors are reported as specified in math_errhandling .

If the argument is less than 1 , a domain error occurs.

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

• If the argument is less than 1, FE_INVALID is raised an NaN is returned.
• If the argument is 1, +0 is returned.
• If the argument is +∞, +∞ is returned.
• If the argument is NaN, NaN is returned.

Notes

Although the C standard names this function "arc hyperbolic cosine", 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 cosine" (used by POSIX) or "area hyperbolic cosine".

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("acosh(1) = %f\nacosh(10) = %f\n", acosh(1), acosh(10));
    printf("acosh(DBL_MAX) = %f\nacosh(Inf) = %f\n", acosh(DBL_MAX), acosh(INFINITY));
 
    // error handling
    errno = 0; feclearexcept(FE_ALL_EXCEPT);
    printf("acosh(0.5) = %f\n", acosh(0.5));
    if (errno == EDOM)
        perror("    errno == EDOM");
    if (fetestexcept(FE_INVALID))
        puts("    FE_INVALID raised");
}

acosh(1) = 0.000000
acosh(10) = 2.993223
acosh(DBL_MAX) = 710.475860
acosh(Inf) = inf
acosh(0.5) = -nan
    errno == EDOM: Numerical argument out of domain
    FE_INVALID raised

References

See also

External links