Answer
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Work Step by Step
The angle $-13\pi$ teminates on the negative x-axis.
Note that the value of tangent of an angle whose terminal side is the negative x-axis is $0$.
Recall:
$\cot{\theta} = \dfrac{1}{\tan{\theta}}$
Thus,
$\cot{(-13\pi)} = \dfrac{1}{\tan{-13\pi}}=\dfrac{1}{0}, \text{ undefined}$