a branch of vector calculus in which operations on helices are studied. Here, a helix is a pair of vectors {a, b} applied at the origins to one point O and satisfying the following conditions: in the transition to a new point O′, vector a does not vary and vector b is replaced by vector b′ = b − [p, a], where p = OO′. The concept of a helix is used in mechanics (the resultant f of the system of forces f1 and the principal moment m of this system with respect to a point in the system form the helix {f, m}) and in geometry (in the theory of linear surfaces). Helical calculus was created in 1895 by the Russian mathematician A. P. Kotel’nikov.