=\left|\begin{array}{ccc}\cos \frac{\theta}{2} & 1 & 1 \\ 1 & \cos \frac{\theta}

\( \operatorname{tet} f(\theta)=\left|\begin{array}{ccc}\cos \frac{\theta}{2} & 1 & 1 \\ 1 & \cos \frac{\theta}{2} & -\cos \frac{\theta}{2} \\ -\cos \frac{\theta}{2} & 1 & -1\end{array}\right| \) \( f(\pi)+f(-\pi) \) is equal to

• A. The maximum value of \( f(\theta) \)
• B. The minimum value of \( f(\theta) \)
• C. Average value of the range of \( f(\theta) \)
• D. None of these