Question

помогите пожалуйста

Answer 1

$cos \alpha = - \frac{ \sqrt{5} }{4}$
$sin \alpha = \sqrt{1 - {cos}^{2} \alpha }$
$sin \alpha = \sqrt{1 - ( { \frac{ ( \sqrt{5}}{4} )}^{2}} = \\ = \sqrt{1 - \frac{5}{16} } = \sqrt{ \frac{11}{16} } = \frac{ \sqrt{11} }{4}$
$tg \alpha = \frac{sin \alpha }{cos \alpha } \\ tg \alpha = \frac{ \sqrt{11} }{4} \div ( - \frac{ \sqrt{5} }{4} ) = \\ = - \frac{ \sqrt{11} }{4} \times \frac{4}{ \sqrt{5} } = - \frac{ \sqrt{11} }{ \sqrt{5} } = - \frac{ \sqrt{55} }{5}$