Помогите решить sin(arctg (-1/3) - 5п/2) = ?

sin (arctg (-1/3) - 5п/2) = -sin (5п/2 + arctg 1/3) = -sin(п/2 + arctg 1/3) = -cos(arctg 1/3) = -3/√10 = -3√10/10