If $f(\sin x) - f(-\sin x) = x^2-1$ is defined for all real x, then the value of $x^2 - 2$ can be ____.

-1

We have, $f(\sin x) - f(-\sin x) = x^2-1$  ...(i) Replacing x by - x, we get $f (- \sin x) - f (\sin x) = x^2 -1$  ...(ii) Adding (i) and (ii), we get $2(x^2-1)=0⇒ x^2-1=0⇒x^2-2=-1$