3.14 12 tg 120° ctg (-480°)

12 * tg(120°) * ctg(-480°) = 12 * tg(180° - 60°) * ctg(-480°+2*360°) = 12 * (-tg(60°)) * ctg(240°) = 12 * (-√3) * ctg(180° + 60°) = 12 * (-√3) * ctg(60°) = 12*(-√3)*(1/√3) = -12