Take the 2-minute tour ×
TeX - LaTeX Stack Exchange is a question and answer site for users of TeX, LaTeX, ConTeXt, and related typesetting systems. It's 100% free, no registration required.

does anyone know, why do I keep getting this error message?

!You cant use '\eqno' in math mode.

..and it's pointing at this line in my code:

\left(\sqrt[5]{x^4}\right)’ &=& \left(x^{[\frac{4}{5}\]}\right)’ &=& [\frac{4}{5}\]x^{[-\frac{1}{5}\]} &=& [\frac{4}{5\sqrt[5]{x}\}] \label{rovnice3} \\

here's the whole array:

\begin{eqnarray}
\int_a^b f(x)\,\mathrm{d}x &=& -\int\limits_b^a f(x)\,\mathrm{d}x \label{rovnice2}\\
\left(\sqrt[5]{x^4}\right)’ &=& \left(x^{[\frac{4}{5}\]}\right)’ &=& [\frac{4}{5}\]x^{[-\frac{1}{5}\]} &=& [\frac{4}{5\sqrt[5]{x}\}] \label{rovnice3} \\    \overline{\overline{A \lor B}} &=& \overline{\overline{A} \land \overline{B}\label{rovnice4} \end{eqnarray}

Thanks in advance!

share|improve this question
2  
LatexGirl, please provide the community with minimal working example (MWE) that replicates your current problem. You problem may be solved using \mbox{\eqno..}, but without more detail it's difficult to say. –  Werner Mar 26 at 21:14
    
I can't reproduce the error you mention. I can see problems with your code, though. 1. In the context you are using them, you don't need \ before ] or }. 2. You are missing a close brace in the last part of the equation. 3. You can only have two ampersands per line in an eqnarray. –  Ian Thompson Mar 26 at 21:24
    
@IanThompson oh I just answered on four & but didn't spot the \] If you want to answer I'll delete mine, or I'll add that to mine, –  David Carlisle Mar 26 at 21:27
    
@DavidCarlisle --- I'm not sure my comment amounts to an answer, because I can't reproduce the original error. Let's wait and see what the OP says when she returns. –  Ian Thompson Mar 26 at 21:30

2 Answers 2

There are some issues:

  • \] instead of ]. \] is the end of an unnumbered equation and interferes with the current environment.

  • \} instead of }, also a missing }, both causing errors, because the group/argument braces are not properly nested.

  • ` instead of '. The short form of ^{\prime} is the ASCII apostrophe (decimal 37, hexadecimal 0x27).

  • eqnarray only supports two &. Only the second equation line has more than one relational symbol, thus at most the first equal sign needs to be aligned.

The following example tries to fix the various issues. Also a variant with align of amsmath is added that also removes some unnecessary delimiters:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{eqnarray}
  \int_a^b f(x)\,\mathrm{d}x
  &=&
  -\int\limits_b^a f(x)\,\mathrm{d}x
  \label{rovnice2}
\\
  \left(\sqrt[5]{x^4}\right)'
  &=&
  \left(x^{\left[\frac{4}{5}\right]}\right)'
  =
  \left[\frac{4}{5}\right]x^{\left[-\frac{1}{5}\right]}
  =
  \left[\frac{4}{5\sqrt[5]{x}}\right]
  \label{rovnice3}
\\
  \overline{\overline{A \lor B}}
  &=&
  \overline{\overline{A} \land \overline{B}}
  \label{rovnice4}
\end{eqnarray}

\begin{align}
  \int_a^b f(x)\,\mathrm{d}x
  &=
  -\int\limits_b^a f(x)\,\mathrm{d}x
  \label{rovnice2b}
\\
  \left(\sqrt[5]{x^4}\right)'
  &=
  \left(x^{\left[\frac{4}{5}\right]}\right)'
  =
  \frac{4}{5}x^{-\frac{1}{5}}
  =
  \frac{4}{5\sqrt[5]{x}}
  \label{rovnice3b}
\\
  \overline{\overline{A \lor B}}
  &=
  \overline{\overline{A} \land \overline{B}}
  \label{rovnice4b}
\end{align}
\end{document}

Result

share|improve this answer
    
Thank you very much! I fixed the problems and now it's working as it should :) –  LatexGirl Mar 26 at 22:10

Please always post complete documents but in an eqnarray you can only have two & per line you have

 &=& [\frac{4}{5}\]x^{[-\frac{1}{5}\]} &=& [\fr

so that is four &

But basically you should never use eqnarray always use align and similar environments from amsmath.

share|improve this answer
    
There are other problems as well: Use of \] inside the environment; and no closing brace for the last \overline{ construction. –  Werner Mar 26 at 21:27

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.