## Trigonometry 7th Edition

$sec120^{\circ}$ = -2
Recall: $\sec\theta$ = $\frac{1}{\cos\theta}$ Substitute: $\sec120^{\circ}$ = $\frac{1}{\cos120^{\circ}}$ Simplify: $\sec120^{\circ}$ = $\frac{1}{\frac{-1}{2}}$ $\sec120^{\circ}$ = $\frac{1}{1}$ $\times$ $\frac{2}{-1}$ $\sec120^{\circ}$ = -2