Question

вопрос по алгебре 2 задания 25 баллов

Answer 1

$sina=-frac{1}{sqrt3}, ; 180^o textless a textless 270^o\cosa=-sqrt{1-(-frac{1}{sqrt3})^2}=-sqrt{frac{2}{3}}\\sin2a=2sinacosa\2*(-frac{1}{sqrt3})*(-frac{sqrt2}{sqrt3})=frac{2sqrt2}{3};\\\frac{cos2a}{sina*cosa+sin^2a}=ctga-1\frac{cos^2a-sin^2a}{sina(cosa+sina)}=frac{(cosa-sina)(cosa+sina)}{sina(cosa+sina)}=frac{cosa-sina}{sina}=\frac{cosa}{sina}-frac{sina}{sina}=ctga-1.$