I am getting an error message when I try to use the multline environment inside cases. This is my equation:

\begin{equation} \label{eq:SMSKIN_TU2009} 
        SM_{SKIN,Int} &= SM_{SKIN,Old} + INI - Q_M - EA_{SKIN} + SM_{SKIN,Upd} \\
        SM_{SKIN,New} &= 
            FC_{SKIN}     & 
                \quad \text{if } SM_{SKIN,Int} > FC_{SKIN}, \quad Q_{SKIN} = SM_{SKIN,Int} - \\ FC_{SKIN}
            \end{multline} \\
            0             & \quad \text{if } SM_{SKIN,Int} < 0,  \quad Q_{SKIN} = 0\\
            SM_{SKIN,Int} & \quad \text{otherwise },  \quad Q_{SKIN} = 0\\

If I don't use the multline environment, the equation is correctly displayed but the compiler throws a warning since the line doesn't fit the page.

I appreciate all your help. Thanks!

  • 2
    It should not use multline in any case, try aligned probably best with the [t] option – daleif Aug 2 '19 at 14:05
  • aligned also shows errors... can you please provide a more explicit answer @daleif ? – Rodolfo Aug 2 '19 at 14:21
  • 1
    Aligned works just fine, would you please provide a full minimal example including preamble and document class, I just added document class and amsmath and replaced multline with aligned, compiles out of the box. – daleif Aug 2 '19 at 14:25
  • 3
    You might also want to have a look at the mathtools package and at its multlined environment. – GuM Aug 2 '19 at 15:39

As @GuM has suggested, you could load the mathtools package (a superset of the amsmath package) and use its multlined environment instead of the illegal multline environment However, I think you're better off using a simple \parbox to display the material in question.

I would also use \mathit to typeset the multi-letter variable names and \mathrm to typeset the acronyms placed in the subscripts.

enter image description here

\usepackage{mathtools} % for 'dcases' env.
\begin{equation} \label{eq:SMSKIN_TU2009} 
&= \mathit{SM}_{\mathrm{SKIN},\mathrm{Old}} + \mathit{INI} 
   - Q_M - \mathit{EA}_{\mathrm{SKIN}} 
   + \mathit{SM}_{\mathrm{SKIN},\mathrm{Upd}} \\
&= \begin{dcases}
         %% set up a parbox with automatic hanging indentation from the 2nd line onward
           if $\mathit{SM}_{\mathrm{SKIN},\mathrm{Int}} 
              > \mathit{FC}_{\mathrm{SKIN}}$, 
           $Q_{\mathrm{SKIN}} = 
              - \mathit{FC}_{\mathrm{SKIN}}$} \\
      0 & \text{if $\mathit{SM}_{\mathrm{SKIN},\mathrm{Int}} < 0$,   
         $Q_{\mathrm{SKIN}} = 0$}\\
         & \text{otherwise,  $Q_{\mathrm{SKIN}} = 0$}
| improve this answer | |
  • 1
    thanks a lot @Mico, that's exactly how I wanted to display it. – Rodolfo Aug 3 '19 at 16:34

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