Answer
Undefined.
Work Step by Step
$\cot [n\cdot 180^{\circ}]=\frac{\cos[n\cdot180^{\circ}]}{\sin[n\cdot180^{\circ}]}$
$\cos[n\cdot180^{\circ}]$ can either be equal to 1 or -1.
But $\sin [n\cdot 180^{\circ}]=0$
As denominator vanishes, $\cot[ n\cdot 180^{\circ}]$ is undefined.
