acos, acosf, acosl - arc cosine function

       For an explanation of the terms used in this section, see attributes(7).
       ┌─────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                                                                   │ Attribute     │ Value   │
       ├─────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │ acos(), acosf(), acosl()                                                    │ Thread safety │ MT-Safe │
       └─────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

       These functions calculate the arc cosine of x; that is the value whose cosine is x.

       See math_error(7) for information on how to determine whether an error has occurred  when  calling  these
       functions.

       The following errors can occur:

       Domain error: x is outside the range [-1, 1]
              errno is set to EDOM.  An invalid floating-point exception (FE_INVALID) is raised.

       C99, POSIX.1-2001.

       The variant returning double also conforms to C89, SVr4, 4.3BSD.

       Math library (libm, -lm)

       acos, acosf, acosl - arc cosine function

       On  success,  these  functions  return  the  arc cosine of x in radians; the return value is in the range
       [0, pi].

       If x is a NaN, a NaN is returned.

       If x is +1, +0 is returned.

       If x is positive infinity or negative infinity, a domain error occurs, and a NaN is returned.

       If x is outside the range [-1, 1], a domain error occurs, and a NaN is returned.

asin(3), atan(3), atan2(3), cacos(3), cos(3), sin(3), tan(3)

Linux man-pages 6.9.1                              2024-05-02                                            acos(3)

       C11, POSIX.1-2008.

#include<math.h>doubleacos(doublex);floatacosf(floatx);longdoubleacosl(longdoublex);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       acosf(), acosl():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE