$\displaystyle \frac{\sqrt{3}}{3}$\displaystyle \frac{\sqrt{3}}{3}

$\displaystyle \frac{\sqrt{6}}{3}$\displaystyle \frac{\sqrt{6}}{3}

$\displaystyle \frac{\sqrt{2}}{2}$\displaystyle \frac{\sqrt{2}}{2}

$\displaystyle \frac{\sqrt{6}}{2}$\displaystyle \frac{\sqrt{6}}{2}