Answer
$2-\sqrt3$.
Work Step by Step
We know that $\tan(A/2)=\frac{1-\cos A}{\sin A}$.
Hence here $\tan(\pi/12)=\frac{1-\cos \pi/6}{\sin \pi/6}=\frac{1-\frac{\sqrt3}{2}}{0.5}=2-\sqrt3$.
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