Answer
$\cot 390^{\circ}$ = 1.7321
Work Step by Step
Using calculator in degree mode-
390 → $\tan$ → $\frac{1}{x}$ (Recall $\cot\theta$ = $\frac{1}{\tan\theta}$)
$\cot 390^{\circ}$ = 1.7320508076
Rounding it to four places past the decimal point-
$\cot 390^{\circ}$ = 1.7321