Answer
$a.\qquad-1 \\$
$b. \qquad -\sqrt{2} \\$
$c. \qquad -1$
Work Step by Step
$ a. \displaystyle \qquad \tan(-\frac{\pi}{4})=\qquad$... even/odd properties,
$=-\displaystyle \tan(\frac{\pi}{4})=\qquad$...table p.410...
$=-1$
$ b. \displaystyle \qquad \csc(-\frac{\pi}{4})=\qquad$... even/odd properties,
$=-\displaystyle \csc(\frac{\pi}{4})\qquad$...table p.410...
$=-\sqrt{2}$
$ c. \displaystyle \qquad \cot(-\frac{\pi}{4})=\qquad$... even/odd properties,
$=-\displaystyle \cot(\frac{\pi}{4})=\qquad$...table p.410...
$=-1$