Matrices And Determinants

Let $A$ be a $3 \times 3$ matrix with real entries such that

$$ A=\left[\begin{array}{ccc} 4 & -1 & \cos x \\ -1 & 5 x & 25 \\ x^2+1 & 25 & 7 \end{array}\right] $$

For how many values of $x$, the matrix $A$ is symmetric?