## Trigonometry 7th Edition

$60^{\circ}$
Supplement of $120^{\circ}$ 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 $60^{\circ}$. Another way to find supplement of an angle will be to subtract it from $180^{\circ}$. Hence supplement of $120^{\circ}$ = $180^{\circ}$- $120^{\circ}$ = $60^{\circ}$