  In this part of the series I show how five-tensors can be used for describing
in a coordinate-independent way finite and infinitesimal Poincare
transformations in flat space-time. As an illustration, I reformulate the
classical mechanics of a perfectly rigid body in terms of the analogs of
five-vectors in three-dimensional Euclidean space. I then introduce the notion
of the bivector derivative for scalar, four-vector and four-tensor fields in
flat space-time and calculate its analog in three-dimensional Euclidean space
for the Lagrange function of a system of several point particles in classical
nonrelativistic mechanics.
