atan2(3) Library Functions Manual atan2(3) atan2, atan2f, atan2l - c LIBRARY Math library (libm, -lm) #include double atan2(double y, double x); float atan2f(float y, float x); long double atan2l(long double y, long double x); glibc (. feature_test_macros(7)): atan2f(), atan2l(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE y/x; . y/x ; [-pi, pi]. y +0 (-0) x 0, +pi (-pi). y +0 (-0) x 0, +0 (-0). y 0 x +0 -0, -pi/2. y 0 x +0 -0, pi/2. x y NaN, NaN. x +0 (-0) x -0, +pi (-pi). x +0 (-0) x +0, +0 (-0). y -- () 0 x , +pi (-pi). y -- () 0 x , +0 (-0). y ( ) x , pi/2 (-pi/2). y ( ) x , +3*pi/4 (-3*pi/4). y ( ) x , +pi/4 (-pi/4). . attributes(7). +----------------------------+----------------------------------------------------------+--------------------------+ | | | | +----------------------------+----------------------------------------------------------+--------------------------+ |atan2(), atan2f(), atan2l() | | MT-Safe | +----------------------------+----------------------------------------------------------+--------------------------+ C11, POSIX.1-2008. C99, POSIX.1-2001. , double, SVr4, 4.3BSD, C89. . acos(3), asin(3), atan(3), carg(3), cos(3), sin(3), tan(3) Dmitry Bolkhovskikh Yuri Kozlov ; GNU 3 , . . , , . Linux man-pages 6.06 31 2023 . atan2(3)