Answer
$\approx \ -0.59$
Work Step by Step
We know that $\cot {x}=\dfrac{1}{\tan{(x)}}$.
This can also be written as: $\cot^{-1}{x}=\tan^{-1} (\dfrac{1}{x})$
In order to get the answer in radians, we need to set the calculator in radians mode and round the result to two decimal places to obtain:
$\cot^{-1}(-\dfrac{3}{2})=\tan^{-1} (\dfrac{1}{ -3/2}) \approx \ -0.59$