$\displaystyle \cos^2\alpha= \frac{1}{6}$\displaystyle \cos^2\alpha= \frac{1}{6}

$\displaystyle \cos^2\alpha= \frac{1}{5}$\displaystyle \cos^2\alpha= \frac{1}{5}

$\displaystyle \cos^2\alpha= \frac{\sqrt{5}}{5}$\displaystyle \cos^2\alpha= \frac{\sqrt{5}}{5}

$\displaystyle \cos^2\alpha= \frac{5}{6}$\displaystyle \cos^2\alpha= \frac{5}{6}