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.nf |
.b #include <math.h> |
.pp |
.bi "double acos(double " x ); |
.bi "float acosf(float " x ); |
.bi "long double acosl(long double " x ); |
.fi |
.pp |
link with \fi\-lm\fp. |
.pp |
.rs -4 |
feature test macro requirements for glibc (see |
.br feature_test_macros (7)): |
.re |
.pp |
.br acosf (), |
.br acosl (): |
.nf |
_isoc99_source || _posix_c_source >= 200112l |
|| /* since glibc 2.19: */ _default_source |
|| /* glibc <= 2.19: */ _bsd_source || _svid_source |
.fi |
.sh description |
these functions calculate the arc cosine of |
.ir x ; |
that is |
the value whose cosine is |
.ir x . |
.sh return value |
on success, these functions return the arc cosine of |
.ir x |
in radians; the return value is in the range [0,\ pi]. |
.pp |
if |
.i x |
is a nan, a nan is returned. |
.pp |
if |
.i x |
is +1, |
+0 is returned. |
.pp |
if |
.i x |
is positive infinity or negative infinity, |
a domain error occurs, |
and a nan is returned. |
.pp |
if |
.i x |
is outside the range [\-1,\ 1], |
a domain error occurs, |
and a nan is returned. |
.sh errors |
see |
.br math_error (7) |
for information on how to determine whether an error has occurred |
when calling these functions. |
.pp |
the following errors can occur: |
.tp |
domain error: \fix\fp is outside the range [\-1,\ 1] |
.i errno |
is set to |
.br edom . |
an invalid floating-point exception |
.rb ( fe_invalid ) |
is raised. |
.sh attributes |
for an explanation of the terms used in this section, see |
.br attributes (7). |
.ad l |
.nh |
.ts |
allbox; |
lbx lb lb |
l l l. |
interface attribute value |
t{ |
.br acos (), |
.br acosf (), |
.br acosl () |
t} thread safety mt-safe |
.te |
.hy |
.ad |
.sp 1 |
.sh conforming to |
c99, posix.1-2001, posix.1-2008. |
.pp |
the variant returning |
.i double |
also conforms to |
svr4, 4.3bsd, c89. |
.sh see also |
.br asin (3), |
.br atan (3), |
.br atan2 (3), |
.br cacos (3), |
.br cos (3), |
Subsets and Splits