Question

Вычислите cos a, tg a, ctg a, если sin a = -4/5, п

Answer 1

сos²(a) + sin²(a) = 1,  

⇵  ⇵ 

сos(a) = √1 - sin²(a),

сos(a) = √1 - (-4/5)² = √1 - 16/25 = √25/25 - 16/25 = √9/25 = 3/5,

tg(a) = sin(a) / cos(a),

tg(a) = (-4/5) / (3/5) = -4/5 * 5/3 = -4/3 = - 1 1/3,

ctg(a) = cos(a) / sin(a),

ctg(a) = (3/5) / (-4/5) = -3/5 * 5/4 = - 3/4