Используя свойство периодичности функции f (x) = cos x, найдите: a) cos 13pi/6 6) cos 19pi/3 B) cos 33pi/4 г) cos 11pi

Используем периодичность косинуса: cos(x + 2πk) = cos x.

а) cos(13π/6) = cos(2π + π/6) = cos(π/6) = √3/2

б) cos(19π/3) = cos(6π + π/3) = cos(π/3) = 1/2

в) cos(33π/4) = cos(8π + π/4) = cos(π/4) = √2/2

г) cos(11π) = cos(5·2π + π) = cos(π) = -1