I am in math mode and I would like to push text (that justifies a step in an equation) to the end of the page. Usually I would apply "Horizontal Fill"; however, this option is removed when I am in math mode. For example, I would like to push the expression (by (3)) to the margin of the page.

enter image description here

Here is the source for my chain of equations.

\text{Hdim}K_{0}\left(\theta\right) & \le &           
\limsup_{i\to\infty}\frac{\log\#\sigma\left(\alpha\right)}{\log n_{k_{i}+1}-\log       
& = & \limsup_{i\to\infty}\frac{\log a_{k_{i}+1}}{\log n_{k_{i+1}}-\log   
n_{k_{i}}}\qquad\left(\text{by }\left(3\right)\right)

MWE: I would like expressions used to justify steps in a chain of equations/inequalities to appear on the right margin just as (3) does in the following pdf imageenter image description here

Here is the Latex Source for this example.

\textup{Let $\alpha\in J$ and $k=\left|\alpha\right|$.} 
\#\sigma\left(\alpha\right)\le a_{k+1}
  • Well actually your caption don't let me see well the equations for understand better your issue. Could you bring us a Minimal Working Example of your document for understand you better?
    – Aradnix
    Apr 29, 2014 at 2:17
  • I've added the Latex Source from my LyX document. Apr 29, 2014 at 2:25
  • I asked for a whole minimal working example, not only a portion of the document, but I see you don't use the amsmathpackage or another that improve and ease the work with mathematical equations. I have few ideas, but without a MWE perhaps will be better wait.
    – Aradnix
    Apr 29, 2014 at 23:19

1 Answer 1


Use the \tag* macro from amsmath:


y &= f(x) \tag*{foo}


You can insert it inside LyX with Ctrl-L (Eval Red Text) as LaTeX code: LyX inserts the backslash and insert tag*{foo} which will then be collapsed to:

enter image description here

However, do not use the environment eqnarray, it has a lousy formatting. Use environment align instead.

  • Where should the code be inserted, and does it start at \begin or \documentclass{article}? My document class is aricle, and I included the \usepackage{amsmath} to my latex preamble, but I am not sure where/how to implement this. I'm not sure if ERT works in math mode, and I cannot generate a pdf when I paste this code in ERT. Apr 30, 2014 at 6:23
  • 1
    Write your equation as usual and at the end of the equation
    – user2478
    Apr 30, 2014 at 6:40
  • Herbert, I see how to use this code if my chain of equalities is 1 line, but where to I insert this code if I have a vertical chain of equalities and I want "foo" to appear in one of the rows? Apr 30, 2014 at 11:06
  • then at the end of that row
    – user2478
    Apr 30, 2014 at 17:22

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