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ACOS(3) Linux Programmer's Manual ACOS(3)NAMEacos, acosf, acosl - arc cosine functionSYNOPSIS#include<math.h>doubleacos(doublex);floatacosf(floatx);longdoubleacosl(longdoublex);Link with-lm. Feature Test Macro Requirements for glibc (see feature_test_macros(7)):acosf(),acosl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; orcc-std=c99DESCRIPTIONTheacos() function calculates the arc cosine ofx; that is the value whose cosine isx.RETURNVALUEOn success, these functions return the arc cosine ofxin radians; the return value is in the range [0, pi]. Ifxis a NaN, a NaN is returned. Ifxis +1, +0 is returned. Ifxis positive infinity or negative infinity, a domain error occurs, and a NaN is returned. Ifxis outside the range [-1, 1], a domain error occurs, and a NaN is returned.ERRORSSee math_error(7) for information on how to determine whether an error has occurred when calling these func- tions. The following errors can occur: Domain error:xis outside the range [-1, 1]errnois set toEDOM. An invalid floating-point exception (FE_INVALID) is raised.CONFORMINGTOC99, POSIX.1-2001. The variant returningdoublealso conforms to SVr4, 4.3BSD, C89.SEEALSOasin(3), atan(3), atan2(3), cacos(3), cos(3), sin(3), tan(3)COLOPHONThis page is part of release 3.22 of the Linuxman-pagesproject. A description of the project, and informa- tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. 2008-08-05 ACOS(3)