$f(x)=\begin {vmatrix} 2 \cos x & 1 & 0 \\ x-\frac{\pi}{2} & 2 \cos x & 1 \\ 0 & 1 & 2 \cos x \end {vmatrix}=>f'(\pi)=$

Question

\[\begin {array} {1 1} (1)\;0 & \quad (2)\;2 \\ (3)\;\frac{\pi}{2} & \quad (4)\;\pi-6 \end {array}\]