Answer
$45^{\circ}$
Work Step by Step
Complement of $45^{\circ}$ will be another angle that terminal side needs to sweep in order to reach position y i.e. standard position of $90^{\circ}$.
Obviously it will be $45^{\circ}$.
Another way to find complement of an angle will be to subtract it from $90^{\circ}$.
Hence complement of $45^{\circ}$ = $90^{\circ}$- $45^{\circ}$ = $45^{\circ}$
