Two vectors are $( \overrightarrow A + \overrightarrow B)$ and $( \overrightarrow A - \overrightarrow B)$. The angle between their resultant vector and $ \overrightarrow A $ is :

Question

$\begin {array} {1 1} (1)\;\cos^{-1}\:( A/B) & \quad (2)\;\cos^{-1} (B/A) \\ (3)\;\cos^{-1} \bigg( \large\frac{A-B}{A+B} \bigg) & \quad (4)\;Zero \end {array}$