acos(3) Library Functions Manual acos(3) acos, acosf, acosl - LIBRARY Math library (libm, -lm) #include double acos(double x); float acosf(float x); long double acosl(long double x); glibc (. feature_test_macros(7)): acosf(), acosl(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE x; x. x ; [0, pi]. x NaN, NaN. x +1, +0. x , , NaN. x [-1, 1], , NaN. math_error(7), , . : : x [-1, 1] errno EDOM. (FE_INVALID). attributes(7). +----------------------------+----------------------------------------------------------+--------------------------+ | | | | +----------------------------+----------------------------------------------------------+--------------------------+ |acos(), acosf(), acosl() | | MT-Safe | +----------------------------+----------------------------------------------------------+--------------------------+ C11, POSIX.1-2008. C99, POSIX.1-2001. The variant returning double also conforms to C89, SVr4, 4.3BSD. . asin(3), atan(3), atan2(3), cacos(3), cos(3), sin(3), tan(3) Dmitry Bolkhovskikh Yuri Kozlov ; GNU 3 , . . , , . Linux man-pages 6.06 31 2023 . acos(3)