Odpowiedź:
[tex] \cos \alpha = - \frac{3}{5} \\ \\ { \sin}^{2} \alpha + { \cos}^{2} \alpha = 1 \\ ( { - \frac{3}{5} })^{2} + { \cos}^{2} \alpha = 1 \\ \frac{9}{25} + { \cos }^{2} \alpha = 1 \\ { \cos }^{2} \alpha = \frac{16}{25} \\ \cos \alpha = \sqrt{ \frac{16}{25} } = \frac{4}{5} \\ \\ tg \alpha = \frac{sin \alpha }{cos \alpha } = \frac{ - \frac{ 3}{5} }{ \frac{4}{5} } = - \frac{3}{5} \times \frac{5}{4} = - \frac{3}{4} [/tex]
