1. Вычислить, отметив угол на окружности: a) cos 510°; б) sin 19π/6; в) cos(-11π/3); г) tg 11π/6; д) ctg(-13π/4)

a) cos 510° = cos(510° - 360°) = cos 150° = -√3/2.
б) sin(19π/6) = sin(3π + π/6) = sin(π + π/6) = -sin(π/6) = -1/2.
в) cos(-11π/3) = cos(11π/3) = cos(4π - π/3) = cos(π/3) = 1/2.
г) tg(11π/6) = tg(2π - π/6) = -tg(π/6) = -1/√3 = -√3/3.
д) ctg(-13π/4) = -ctg(13π/4) = -ctg(3π + π/4) = -ctg(π + π/4) = -ctg(π/4) = -1.