
If $x=f(a)$ is solved for $a\in\mathbb Q$ and $f(a)$ is continuous, then $x=f(a)$ for $a\notin\mathbb Q$.
Next, we see that if $a\ne0,a\in\mathbb Q$, then $x$ is not algebraic. If $x$ were algebraic, then $\sin(x)$ would be transcendental, and thus $x\sin(x)$ would be transcendental, a contradi...