Answer
$\color{blue}{\cot{(\frac{5\pi}{6})}=-\sqrt3}$
Work Step by Step
Figure 13 on page 579 of this book shows that the unit circle point $(\frac{-\sqrt3}{2}, \frac{1}{2})$ corresponds to the real number $\dfrac{5\pi}{6}$.
RECALL:
(i) $\cos{s} = x$
(ii) $\sin{s} = y$
(iii) $\tan{s}=\dfrac{y}{x}$
(iv) $\sec{s} =\dfrac{1}{x}$
(v) $\csc{s} = \dfrac{1}{y}$
(vi) $\cot{s} = \dfrac{x}{y}$
Use the coordinates of the unit circle point above and the formula in (v) above to obtain:
$\color{blue}{\cot{(\frac{5\pi}{6})}=\dfrac{\frac{-\sqrt3}{2}}{\frac{1}{2}}=\frac{-\sqrt3}{2} \cdot \frac{2}{1}=-\sqrt3}$
