atan
double atan(double);
using ::atan;
inline float atan(float __X) { return atanf(__X); }
inline long double atan(long double __X) { return atanl(__X); }
extern double atan(double);
D_RE(ans) = atan(y / x);
D_RE(ans) = atan(sqrt(half * Apx * (y2 / (R +
D_RE(ans) = atan((y * sqrt(half * (Apx / (R +
D_RE(ans) = atan(t);
D_RE(ans) = atan(x / sqrt(half * Apx * (y2 /
D_RE(ans) = atan(x / (y * sqrt(half * (Apx /
D_RE(ans) = atan(ax);