Answer
$135^{\circ}$
Work Step by Step
Supplement of $45^{\circ}$ will be another angle that terminal side needs to sweep in order to reach at standard position of $180^{\circ}$. (Figure 24)
Obviously it will be - (45 + 90) i.e. $135^{\circ}$.
Another way to find supplement of an angle will be to subtract it from $180^{\circ}$.
Hence supplement of $45^{\circ}$ = $180^{\circ}$- $45^{\circ}$ = $135^{\circ}$
