Nie istnieje kąt ostry α taki, że:

$\sin\alpha=\dfrac{4}{5}$\sin\alpha=\dfrac{4}{5}, $\cos\alpha=\dfrac{3}{5}$\cos\alpha=\dfrac{3}{5}

$\sin\alpha=\dfrac{12}{13}$\sin\alpha=\dfrac{12}{13}, $\cos\alpha=\dfrac{5}{13}$\cos\alpha=\dfrac{5}{13}

$\sin\alpha=\dfrac{7}{25}$\sin\alpha=\dfrac{7}{25}, $\cos\alpha=\dfrac{24}{25}$\cos\alpha=\dfrac{24}{25}

$\sin\alpha=\dfrac{4}{9}$\sin\alpha=\dfrac{4}{9}, $\cos\alpha=\dfrac{7}{9}$\cos\alpha=\dfrac{7}{9}