[Tex/LaTex] Problem with equation format when starting equation with \dot and \ddot

equationsmath-mode

I am having problems with equation formatting inside the equation environment when the equations begin with \dot or \ddot

When I write:

\begin{equation}

    \ddot{\theta} + \frac{g}{l}\sin(\theta) = 0

\end{equation}

The theta with the dots in the equation does not appear, the formula begins at the left margin and the number appears on the line below.

I am using the book document class with the ams packages and the spanish babel package as well. I am using pdflatex to compile via Texmaker.

Best Answer

A blank line in a display math environment is always disallowed and certainly produces error messages and, possibly, wrong output.

If you prefer to have space in the input, type

\begin{equation}
%
\ddot{\theta} + {\dfrac{g}{l}}\sin(\theta) = 0 
%
\end{equation}

but never leave a blank line there.

Related Solutions

[Tex/LaTex] How to properly display chemical compounds within \equation? (mhchem won’t do what I need)

Your code isn't working as it stands: the second line is not in math mode or inside \ce so _ must issue an error.

Li_{2}(SO_{4})_{0.5}

In the third and fourth line the groups are not balenced but miss a }. After correcting this:

\begin{equation} X_{\ce{Li2(SO4)0.5}} \end{equation}

\begin{equation} X_{\ce{Li2(SO4)_{0.5}}} \end{equation}

the behaviour of the third is documented mhchem behaviour to display adducts so the forth is not a workaround but the way to go.

\documentclass{article}
\usepackage[version=3]{mhchem}
\begin{document}

\ce{Li2(SO4)_{0.5}}

Adduct: \ce{Na2SO4.10H2O}

\begin{equation}
 X_{\ce{Li2(SO4)_{0.5}}}
\end{equation}

\end{document}

enter image description here

Alternatively one can use (my own) chemformula:

\documentclass{article}
\usepackage{chemformula}
\begin{document}

\ch{Li2(SO4)_{0.5}}

Adduct: \ch{Na2SO4 * 10 H2O}

\begin{equation}
 X_{\ch{Li2(SO4)_{0.5}}}
\end{equation}

\end{document}

enter image description here

[Tex/LaTex] Main label in a system of equations

You can use empheq together with amsmath and its subequations environment.

\documentclass{book}
\usepackage{amsmath,empheq}
\usepackage{hyperref}

\begin{document}

\begin{subequations}\label{eq:system}
\begin{empheq}[left=\empheqlbrace]{align}
  &\frac{d\psi}{d\zeta} = \frac{m_1}{y_1'}(x_1-\beta y_1') \label{eq:dpsidz}
  \\
  &\frac{dx_i}{d\zeta} = \frac{m_i}{\psi y_i'}(x_i-y_i')(x_i-\beta y_i')
    \qquad \forall i=1,\dots,C-1 \label{eq:dxdz}
  \\
  &0 = y_1' (x_j-\beta y_j')-\alpha_{1j}y_j'(x_1-\beta y_1')
    \qquad \forall j=2,\dots,C \label{eq:algeb1}
  \\
  &0 = \sum_{i=1}^{C}y_i' -1 \label{eq:algeb2}
  \\
  &\psi|_{\zeta=0} = 1
  \\
  &x_i|_{\zeta=0} = x_i^F \qquad \forall i=1,\dots,C
\end{empheq}
\end{subequations}
The system illustrated in \ref{eq:system} is a \textsc{dae} system 
with a differential index equal to~$1$.

\end{document}

With hyperref the anchor will be immediately above the system.

A couple of stylistic notes:

instead of ... you should input \dots;
instead of \prime you should use ^{\prime} or the easier ' (apostrophe) as in the code above.

Best Answer

Related Solutions

[Tex/LaTex] How to properly display chemical compounds within \equation? (mhchem won’t do what I need)

[Tex/LaTex] Main label in a system of equations

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