  For a single-channel nucleon-nucleon scattering, a well-known and convenient
variable phase approach is considered, which is widely used for practical
problems of atomic and nuclear physics. Approximation of the $pp$- and $np$-
scattering phases obtained for the modern realistic phenomenological
nucleon-nucleon potential Reid93 was carried out. The approximation function is
used as a well-known formula for a parabolic-type quadratic function.
