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ACOSH(3) Linux Programmer's Manual ACOSH(3)NAMEacosh, acoshf, acoshl - inverse hyperbolic cosine functionSYNOPSIS#include<math.h>doubleacosh(doublex);floatacoshf(floatx);longdoubleacoshl(longdoublex);Link with-lm. Feature Test Macro Requirements for glibc (see feature_test_macros(7)):acosh(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE; orcc-std=c99acoshf(),acoshl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; orcc-std=c99DESCRIPTIONTheacosh() function calculates the inverse hyperbolic cosine ofx; that is the value whose hyperbolic cosine isx.RETURNVALUEOn success, these functions return the inverse hyperbolic cosine ofx. Ifxis a NaN, a NaN is returned. Ifxis +1, +0 is returned. Ifxis positive infinity, positive infinity is returned. Ifxis less than 1, a domain error occurs, and the functions return a NaN.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 less than 1errnois set toEDOM. An invalid floating-point exception (FE_INVALID) is raised.CONFORMINGTOC99, POSIX.1-2001. The variant returningdoublealso conforms to SVr4, 4.3BSD, C89.SEEALSOasinh(3), atanh(3), cacosh(3), cosh(3), sinh(3), tanh(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 ACOSH(3)