The angle between vector $(\vec{A})$ and $(\vec{A} - \vec{B})$ is :
(1) $\tan^{-1}\left(\frac{B\cos\theta}{A - B\sin\theta}\right)$
(2) $\tan^{-1}\left(\frac{\sqrt{3}B}{2A - B}\right)$
(3) $\tan^{-1}\left(\frac{-\frac{B}{2}}{A - B\frac{\sqrt{3}}{2}}\right)$
(4) $\tan^{-1}\left(\frac{A}{0.7B}\right)$