Дано: ctgb-11/3 Найдите cosb

1+ctg^2 b=1/sin^2 b1+121/9=1/sin^2 b130/9=1/1/sin^2 bsin^2 b=9/130sin^2 b+cos^2 b=1cos^2 b=1-sin^2 bcos^2 b=1-9/121=112/121cos b=()/11