check ("atan (1) == pi/4", FUNC(atan) (1), M_PI_4); check ("atan (-1) == -pi/4", FUNC(atan) (1), M_PI_4);
check_eps ("atan (1) == pi/4", FUNC(atan) (1), M_PI_4, CHOOSE (1e-18, 0, 0)); check_eps ("atan (-1) == -pi/4", FUNC(atan) (1), M_PI_4, CHOOSE (1e-18, 0, 0));
atan_test (void){  check ("atan (0) == 0", FUNC(atan) (0), 0);  check ("atan (-0) == -0", FUNC(atan) (minus_zero), minus_zero);  check ("atan (+inf) == pi/2", FUNC(atan) (plus_infty), M_PI_2);  check ("atan (-inf) == -pi/2", FUNC(atan) (minus_infty), -M_PI_2);  check ("atan (1) == pi/4", FUNC(atan) (1), M_PI_4);  check ("atan (-1) == -pi/4", FUNC(atan) (1), M_PI_4);  check_eps ("atan (0.7) == 0.610725964...", FUNC(atan) (0.7),	     0.6107259643892086165L, CHOOSE(3e-17L, 0, 0));}