NAME
acos, acosf, acosl - arc cosine function SYNOPSIS
#include
double acos(double x); float acosf(float x); long double acosl(long double x); Link with -lm. Feature Test Macro Requirements for glibc (see featuretestmacros(7)): acosf(), acosl(): BSDSOURCE || SVIDSOURCE || XOPENSOURCE >= 600 || ISOC99SOURCE || POSIXCSOURCE >= 200112L;
or cc -std=c99 DESCRIPTION The acos() function calculates the arc cosine of x; that is the value whose cosine is x. RETURN VALUE 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. ERRORS See matherror(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 (FEINVALID) is raised. ATTRIBUTES For an explanation of the terms used in this section, see attributes(7). ┌─────────────────────────┬───────────────┬─────────┐ │Interface │ Attribute │ Value │ ├─────────────────────────┼───────────────┼─────────┤
│acos(), acosf(), acosl() │ Thread safety │ MT-Safe │ └─────────────────────────┴───────────────┴─────────┘ CONFORMING TO
C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD, C89. SEE ALSO asin(3), atan(3), atan2(3), cacos(3), cos(3), sin(3), tan(3) COLOPHON
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2010-09-20 ACOS(3)