Kąt jest ostry oraz . Wtedy
cosα=525\displaystyle \cos\alpha= \frac{5}{2\sqrt{5}} cosα=255\displaystyle \cos\alpha= \frac{5}{2\sqrt{5}}
cosα=55\displaystyle \cos\alpha= \frac{\sqrt{5}}{5} cosα=55\displaystyle \cos\alpha= \frac{\sqrt{5}}{5}
cosα=15\displaystyle \cos\alpha= \frac{1}{5} cosα=51\displaystyle \cos\alpha= \frac{1}{5}
cosα=45\displaystyle \cos\alpha= \frac{4}{5} cosα=54\displaystyle \cos\alpha= \frac{4}{5}
ed40b1ca-5c62-43cb-9ae6-cd1745d39024
(nowa formuła)
