We can do this by adding multiples of $2\pi$ (which is a full circle in radians) until we get a positive angle. In this case, we add $2\pi$ three times to $-\frac{17\pi}{6}$ to get $\frac{5\pi}{6}$.
$$-\frac{17\pi}{6} = -\frac{12\pi}{6} - \frac{5\pi}{6} = -2\pi -
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