Question: How do I find the sum of all the real roots of a simple trigo equation with MAPLE?

Here is what I tried.

I need to get the sum of all the real roots of 3*sin(x^2) = x

So I tried this. 

>solve(3*sin(x^2)-x = 0, x, AllSolutions)

Which gaved me this 3*sin(RootOf(_Z-9*sin(_Z)^2))

Then >sum(3*sin(RootOf(_Z-9*sin(_Z)^2)), _Z = -infinity .. infinity)

Which gives me this answer which I cannot make sense of.  signum(sin(RootOf(_Z-9*sin(_Z)^2)))*infinity

Can anyone help? Thanks!!!

I need the numerical value and steps :D Thanks a lot.