Equation 14.28.2ACD0920D4D78

\begin{equation} \begin{split} x& =(1-\chi )(p+a)+\chi \sigma ,\\ y& =(1-\chi )(p+b)+\chi (1-\sigma ),\\ z& =1-\chi +\chi \sigma ',\qquad \omega _0=xP+yQ+zR. \end{split} \end{equation}