A vector $\vec { A }$ is rotated by a small angle $\Delta \theta$ radians ( $\Delta \theta \ll 1$ ) to get a new vector $\vec { B }$. In that case $| \vec { B } - \vec { A } |$ is :\\
(1) $| \vec { A } | \left[ 1 - \frac { ( \Delta \theta ) ^ { 2 } } { 2 } \right]$\\
(2) 0\\
(3) $| \vec { A } | \Delta \theta$\\
(4) $| \vec { B } | \Delta \theta - | \vec { A } |$