atan(3) Library Functions Manual atan(3) atan, atanf, atanl - (libm, -lm) #include double atan(double x); float atanf(float x); long double atanl(long double x); glibc (. feature_test_macros(7)): atanf(), atanl(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE x; , x. x ; [-pi/2, pi/2]. x NaN, NaN. x +0 (-0), +0 (-0). x ( ), +pi/2 (-pi/2). . attributes(7). +----------------------------+----------------------------------------------------------+--------------------------+ | | | | +----------------------------+----------------------------------------------------------+--------------------------+ |atan(), atanf(), atanl() | | MT-Safe | +----------------------------+----------------------------------------------------------+--------------------------+ C11, POSIX.1-2008. C99, POSIX.1-2001. , double, SVr4, 4.3BSD, C89. acos(3), asin(3), atan2(3), carg(3), catan(3), cos(3), sin(3), tan(3) () Dmitry Bolkhovskikh , Yuri Kozlov Kirill Rekhov ; GNU (GNU General Public License - GPL, 3 ) , - . - , , () () () <>. Linux 6.9.1 2 2024 . atan(3)