Newbie question, couldn't find an exact dupe.
I'm expecting that with these assumptions
$Assumptions =
Subscript[v, 1] \[Element] Complexes &&
Subscript[v, 2] \[Element] Complexes &&
Subscript[v, 3] \[Element] Complexes &&
Sqrt[Subscript[v, 1]^2 + Subscript[v, 2]^2 + Subscript[v, 3]^2] == 1
The following would be equal to 1
FullSimplify[
Sqrt[Subscript[v, 1]^2 + Subscript[v, 2]^2 + Subscript[v, 3]^2]]
However, I get back
$\sqrt{v_1^2+v_2^2+v_3^2}$
Why?
----- Edit: A simpler version of the question:
Why does the following
FullSimplify[Sqrt[x + y], Assumptions -> Sqrt[x + y] == 1]
evaluate to
Sqrt[x + y]
instead of $1$?
FullSimplify[Sqrt[x + y], Assumptions -> Sqrt[x + y] == 1]
which returnsSqrt[x + y]
. $\endgroup$ – Nasser Dec 2 '18 at 1:12