Is There A Megafunction For Arctan ?

Yes, that was why I recasted the result back to integer, a synthesizable type. I agree that real itself isn't synthesizable, but it's allowed for calculations. I assumed a real input to go into the arctan() function, but if it's a std_logic_vector, we need some kind of conversion to real first.

The arctan() function just serves as the calculation, where it will give a real result (which isn't synthesizable). But we can re-cast this result to integer (or others) that would make it synthesizable?