# FunctionDomain in the Reals numbers [closed]

Why don't I obtain that $x$ belongs to the Reals?

FunctionDomain[x^2 + 4, x]
(* Out: True *)

FunctionDomain[x^2 + 4, x, Reals]
(* Out: True *)


However, there is no problem here:

FunctionDomain[Log[x]/Sqrt[x + y], x]
(* Out: x > 0 && x + y > 0 *)

• True its mean in this case x \[Element] Interval[{-Infinity, Infinity}]. – Mariusz Iwaniuk Jun 21 '18 at 19:18

## 1 Answer

FunctionDomain tells you quantitatively what the domain is:

FunctionDomain[Sqrt[x], x]
(* x >= 0 *)


True just means "no limits" here.