The component of vector $\bar {A}= a_x \hat i + a _y \hat j + a _z \hat k$ along the direction of $\hat i- \hat j$ is

$\begin {array} {1 1} (1)\;a_x-a_y+a_z & \quad (2)\;a_x-a_y \\ (3)\;(a_x-a_y)/ \sqrt 2 & \quad (4)\;(a_x+a_y+a_z) \end {array}$

$(3)\;(a_x-a_y)/ \sqrt 2$