Multline & Splitfrac

Question

\documentclass{article}
\usepackage{amsmath}
\usepackage{mathtools}

\begin{document}
\begin{multline*}
-\dfrac{1}{64\pi^2}
\left[     
      \dfrac{
        \splitfrac{
            (m_2-m_3)(2y_e^2-y_\mu^2-y_\tau^2
              }{
              + (y_\mu^2-y_\tau^2 )\cos2{\theta_{23})\sin\delta^2\sin\theta_{12}^2\sin2\theta_{13}}
              }
        }{
          m_2+m_3
         }\\
    + \dfrac{
      \splitfrac{
              (m_2 + m_3)\cos\delta\sin\theta_{12}(\cos\delta(2y_e^2-y_\mu^2-y_\tau^2 + (y_\mu^2-y_\tau^2 )\cos2\theta_{23})\sin\theta_{12}\sin2\theta_{13}
            }{
            + 2(y_\mu^2-y_\tau^2)\cos\theta_{12}\cos\theta_{13}\sin2\theta_{23})
            }
        }{
          m_2-m_3
         }\\
    + \dfrac{
         \splitfrac{ 
          2(m_1+m_3)\cos\delta\cos\theta_{12}\cos\theta_{13}(\cos\delta\cos\theta_{12}
          }{
        (2y_e^2-y_\mu^2-y_\tau^2 + (y_\mu^2-y_\tau^2 )\cos2\theta_{23})\sin\theta_{13}+(-y_\mu^2+y_\tau^2)\sin\theta_{12}\sin2\theta_{23}
           }
         }{
             m_1-m_3
          }\\
    +\dfrac{1}
             {
              \splitfrac{
                         (m_1+m_3)2(m_1+m_3)\cos\theta_{12}\cos\theta_{13}\sin\delta(y_\mu^2
                        }{
                          -y_\tau^2 )\cos\delta\sin\delta\sin\theta_{12}\sin2\theta_{23}
                         }{
                           +\sin\delta(\cos\theta_{12}(2y_e^2-y_\mu^2-y_\tau^2+(y_\mu^2
                         }{
                            -y_\tau^2)\cos2\theta_{23}\sin\theta_{13}+(-y_\mu^2 + y_\tau^2)\cos\delta\sin\theta_{12}\sin2\theta_{23}
                         }
              }
 \right]            
 \end{multline*}


\end{document}

On compiling this code in KILE it gives the following error

Missing \right.inserted \end{multline*}

Extra \right \end{multline*}

How can I fix this error?

Answer 1

The error is telling you that you have unpaired \left and \right commands. You need to add a \right. and \left. to match the ones on the first and last lines of the environment.

\documentclass{article}
\usepackage{amsmath}
\usepackage{mathtools}

\begin{document}
\begin{multline*}
-\dfrac{1}{64\pi^2}
\left[     
      \dfrac{
        \splitfrac{
            (m_2-m_3)(2y_e^2-y_\mu^2-y_\tau^2
              }{
              + (y_\mu^2-y_\tau^2 )\cos2{\theta_{23})\sin\delta^2\sin\theta_{12}^2\sin2\theta_{13}}
              }
        }{
          m_2+m_3
         }
    \right.%<-------------------HERE
    \\
    + \dfrac{
      \splitfrac{
              (m_2 + m_3)\cos\delta\sin\theta_{12}(\cos\delta(2y_e^2-y_\mu^2-y_\tau^2 + (y_\mu^2-y_\tau^2 )\cos2\theta_{23})\sin\theta_{12}\sin2\theta_{13}
            }{
            + 2(y_\mu^2-y_\tau^2)\cos\theta_{12}\cos\theta_{13}\sin2\theta_{23})
            }
        }{
          m_2-m_3
         }\\
    + \dfrac{
         \splitfrac{ 
          2(m_1+m_3)\cos\delta\cos\theta_{12}\cos\theta_{13}(\cos\delta\cos\theta_{12}
          }{
        (2y_e^2-y_\mu^2-y_\tau^2 + (y_\mu^2-y_\tau^2 )\cos2\theta_{23})\sin\theta_{13}+(-y_\mu^2+y_\tau^2)\sin\theta_{12}\sin2\theta_{23}
           }
         }{
             m_1-m_3
          }\\
    \left. %<-------------------HERE
    +\dfrac{1}
             {
              \splitfrac{
                         (m_1+m_3)2(m_1+m_3)\cos\theta_{12}\cos\theta_{13}\sin\delta(y_\mu^2
                        }{
                          -y_\tau^2 )\cos\delta\sin\delta\sin\theta_{12}\sin2\theta_{23}
                         }{
                           +\sin\delta(\cos\theta_{12}(2y_e^2-y_\mu^2-y_\tau^2+(y_\mu^2
                         }{
                            -y_\tau^2)\cos2\theta_{23}\sin\theta_{13}+(-y_\mu^2 + y_\tau^2)\cos\delta\sin\theta_{12}\sin2\theta_{23}
                         }
              }
 \right]            
 \end{multline*}


\end{document}