Răspuns:
Explicație pas cu pas:
tg x = 2/3
tg x = sinx / cos x
tg² x = sin²x / cos²x = sin²x / (1 - sin²x) = 4/9 =>
9sin²x = 4 - 4 sin²x =>
13sin²x = 4 => sin²x = 4/13 =>
sin x = √(4/13) = 2/√13 = 2√13/13 ≈ 0,555
sin²x = 4/13 => cos²x = 1-4/13 = 9/13 =>
cos x = ±√(9/13) = ±3/√13 = ±3√13/13 ≈ ± 0,832
ctg x = 1/tgx = 3/2
