$\displaystyle \frac{1}{2}$\displaystyle \frac{1}{2}

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

$\displaystyle \frac{\sqrt{3}}{2}$\displaystyle \frac{\sqrt{3}}{2}

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