Question

Найдите cosa, если sinа= -√5110 а∈(3П2; 2П)

Answer 1

при а∈(3П2; 2П):

$cos a=sqrt{1-sin^2 a}=sqrt{1-(frac{-sqrt{51}}{10})^2}=sqrt{frac{100-51}{100}}=sqrt{(frac{7}{10})^2}=frac{7}{10}=0.7$