## Trigonometry (10th Edition)

$\tan$ 45$^{\circ}$ = -1 $\cot$ 45$^{\circ}$ = -1
$\tan$ 45$^{\circ}$ = $\frac{1}{-1}$ = -1 $\cot$ 45$^{\circ}$ = $\frac{-1}{1}$ = -1