How to use isAlways to compare two symbolic equations ?

Dear forum members,

I would like to check wether or not two symbolic equations are the same, but I am not able to do this using isAlways function.

syms a b
f1 = y == abs(x);
f2 = y == sqrt(x^2);
isAlways(f1 == f2)
Warning: Unable to prove '(y == abs(x)) == (y == (x^2)^(1/2))'. 
> In symengine
In sym/isAlways (line 42) 

ans =

  logical

   0

Why do I get these warnings and this (false) answer "logical 0" ? What am I doing wrong ?

Thank you for your help.

Answer 1

[Torsten]

syms x

isAlways(sqrt(x^2)==abs(x))

[CN.]

Thanks for your answer, but I already tested this solution and got the same result :

isAlways(sqrt(x^2)==abs(x))
Warning: Unable to prove '(x^2)^(1/2) == abs(x)'. 
> In symengine
In sym/isAlways (line 42) 

ans =

  logical

   0

[Torsten]

Ok. Then the symbolic toolbox is not able to proove the identity.