CGAL::angle

Angle	angle ( Point_2<R> p, Point_2<R> q, Point_2<R> r)
		returns OBTUSE, RIGHT or ACUTE depending on the angle formed by the three points $$p, $$q, $$r ($$q being the vertex of the angle).
Angle	angle ( Point_3<R> p, Point_3<R> q, Point_3<R> r)
		returns OBTUSE, RIGHT or ACUTE depending on the angle formed by the three points $$p, $$q, $$r ($$q being the vertex of the angle).