acos, acosf, acosl - arc cosine function
#include <math.h> double acos(double x); float acosf(float x); long double acosl(long double x);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
These functions calculate the arc cosine of
x; that is the
value whose cosine is
On success, these functions return the arc cosine of
radians; the return value is in the range [0, pi].
x is a NaN, a NaN is returned.
x is +1, +0 is returned.
x is positive infinity or negative infinity, a domain
error occurs, and a NaN is returned.
x is outside the range [-1, 1], a domain error occurs,
and a NaN is returned.
See math_error(7) for information on how to determine whether an error has occurred when calling these functions.
The following errors can occur:
xis outside the range [-1, 1]
errno is set to EDOM. An invalid
floating-point exception (FE_INVALID) is raised.
C99, POSIX.1-2001, POSIX.1-2008.
The variant returning
double also conforms to SVr4, 4.3BSD,
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