1) Найдите cosa, tga, ctga если sina=-0.8 2) Найдите cosa, tga, ctga если sina=

$cosa = \sqrt{1 - {sin}^{2} a} \\ cosa = \sqrt{1 - {( - 0.8)}^{2} } = \sqrt{1 - 0.64} = \sqrt{0.36} = 0.6 \\ tga = \frac{sina}{cosa} \\ tga = \frac{ - 0.8}{0.6} = - \frac{4}{3} \\ ctga = \frac{cosa}{sina} \\ ctga = \frac{0.6}{ - 0.8} = \frac{3}{4}$

cosa =sqrt(1 - 2/9) =sqrt(7)/3
tga = (sqrt(2)/3)/(sqrt(7)/3) =(sqrt(2))/(sqrt(7))
ctga=(sqrt(7)/3)/(sqrt(2)/3) =(sqrt(7))/(sqrt(2))