College Algebra 7th Edition

$\frac{\sqrt{3}}{3}$
When the denominator has a square root (i.e. $\sqrt{a}$), we multiply the numerator and denominatory by $\sqrt{a}$: $\frac{1}{\sqrt{3}}=\frac{1}{\sqrt{3}}\cdot\frac{\sqrt{3}}{\sqrt{3}}=\frac{\sqrt{3}}{3}$