I want to split up a very long equation. Here is my code:

\text{RBE}(LET_d,D,(\alpha /\beta)_{phot}) = \frac{1}{2D}\cdot
\cdot LET_d\right)^2}

And it looks like this: enter image description here

Thank you in advance!

  • 1
    Welcome to TeX - LaTeX! There are two approaches (a) introduce symbols for subexpressions (b) use building blocks such as aligned from the amsmath package that you already load. Commented Jun 6, 2017 at 14:13
  • 2
    ,@moriambar -- I don't think the duplicate you raised is relevant here because the real problem in the current question is how to split a long square root.
    – AboAmmar
    Commented Jun 6, 2017 at 17:48
  • Related: tex.stackexchange.com/questions/3330 Commented Jun 6, 2017 at 18:20

1 Answer 1


Making use of the multline environment and exploiting the repetition of some big terms; the shortcut $\lambda=(\alpha/\beta)_{phot}$ can be used replacing \lambda with a suitable symbol if it is already used, one can do the following:


\text{RBE}(\LET_d,D,\lambda) = \frac{1}{2D}\times{} \\  
where $\lambda=(\alpha/\beta)_{phot}$


enter image description here

Another possibility (less readable, though) is to use ()^1/2 notation for the square root:

   &= \frac{1}{2D}\biggl[\biggl(\ab^2+4D\ab\Bigl(p_0+\frac{p_l}{(\alpha/\beta)_\text{phot}}\LET_d\Bigr) \notag \\                                                  

enter image description here

  • You should really use \textit{phot} to get better spacing, though the difference is barely visible in this particular case. Commented Jun 6, 2017 at 14:45
  • 1
    @IanThompsom shouldn't it be upright instead. It is likely to be short for photon or similar, written in italics might get it confused with variable subscripts
    – daleif
    Commented Jun 6, 2017 at 15:47

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