Różnica cos^2 67{,}5°-sin^2 67{,}5° jest równa

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

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

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

$0$0