acos
double acos(double);
using ::acos;
inline float acos(float __X) { return acosf(__X); }
inline long double acos(long double __X) { return acosl(__X); }
extern double acos(double);
return ((float)acos((double)x));
D_RE(ans) = acos(x);
D_RE(ans) = acos(x);
D_RE(ans) = acos(B);