Relationships:
                                    (1)  v_s = [v_r² + v_t²]^½,

                                  *(2)  v_t [km/s] = r [km] × µ [rad/s],  or,  v_t [km/s] = 4.74 × r [pc] × µ ["/yr].

                                    (3)  v_r [km/s] = c [km/s] Δλ / λ₀ .

      *v_t[km/s] = r[km]×µ[rad/s]= r[pc]×(3.0857×10¹³ km/pc)×µ["/yr]/(206265 "/rad ×3.1557×10⁷s/yr) = 4.7406 × r[pc] × µ["/yr].