[Tex/LaTex] equation number problem

equationsnumbering

I'm relatively new to TeX/LaTeX, writing classroom notes. here's what I got:

\begin{equation} \label{eqn:constantspeed}
v=\frac{s}{t}
\end{equation}

It is very important to remember that Equation \ref{eqn:constantspeed} only works for objects moving at \emph{constant speed}.

The pdf output has (3.1) as the number on the left side of the page where the equation is but in the text that follows, it shows "Equation 3". Please tell me what I'm doing wrong and how to make the numbers match. Thank you.

Best Answer

The equation number is only 3.1, but the correct referring is (3.1), as you mention. To achieve this, we use \eqref{eqn:constantspeed} instead of \ref{eqn:constantspeed}. As well, in that case we usually omit the word Equation since the parentheses themselves stres that it's an equation reference.

Related Solutions

[Tex/LaTex] Multiply defined labels using hyperref

I've tried using protect and mbox, but nothing works!

Neither will help because they have nothing to do with the references.

The mathmode \label in your document is defined in the following way (most likely by amsmath):

\ifx \df@label \@empty \else \@amsmath@err {Multiple \string \label 's: label
 '\df@label ' will be lost}\@eha \fi \gdef \df@label

i.e., it simply stores the label in \df@label but checks first if it is still empty. Then later, at the end of the equation, it is finally used.

What you need for your extra labels is IMHO the textmode \label. The following code seems to work. Note that I saved away the \label to \textlabel and use a group to keep the change to \@currentlabel local. (Do not use { } or \bgroup \egroup for this because they create a new math atom in mathmode.) Without the group both actually independent labels will interact which each other, i.e. in your example the romeo label will be also have the number 3, not 1.

\let\textlabel\label
\newcommand{\refeq}[1]{%
 \begingroup
 \refstepcounter{qc}\textlabel{#1}%
 \stackrel{
  \stackrel{
   {\text{\tiny $\mathclap{\roman{qc}}$}}
  }{\text{$\downarrow$}}
 }{=}%
 \endgroup
}

Just replace your definition of \refeq with this one. You might also have a look on \hyperlink and \hypertarget (IIRC) to manually add hyperlinks.

[Tex/LaTex] Typesetting a pattern matching equation

Without an image of exactly how you want this typeset it is difficult to know for sure, but perhaps one of these is what you are looking for:

enter image description here

or perhaps:

enter image description here

\documentclass{book}
\usepackage{amsmath}
\newcommand{\fib}{\mathrm{fib}}

\begin{document}
\begin{align*}
    &\text{if }  x < 2 & \fib X &= 1 \\
    &\text{otherwise } & \fib X &= (\fib (X - 1)) + (\fib (X - 2))
\end{align*}
Another option is:
\begin{align*}
\fib X = \begin{cases}
    \text{if }  x < 2 & = 1 \\
    \text{otherwise } & = (\fib (X - 1)) + (\fib (X - 2))
\end{cases}
\end{align*}
\end{document}

Here is how you can modify the given MWE to obtain better spacing:

enter image description here

Notes:

@{} is used to eliminate the inter column spacing
I added {} before the = to get proper math spacing.
I replaced the $$ ... $$ with \[ ... \]. See Why is \[ ... \] preferable to $$ ... $$? for more details.
Changes as per egreg's suggestions:
1. \mathit{foreign}, \mathit{time\_of\_call} and \mathrm{head} for better appearance of the formulas.
2. Removed \, after \prodtime, and the other uses of \operatorname.

Code:

\documentclass{article}
\usepackage{amsmath}

\newcommand{\prodtime}{\operatorname{prodtime}}

\begin{document}
\[
\begin{array}{l l @{}l}
\prodtime V & X = Y                        &{}= 0 \\
\prodtime V & X = f(\ldots)                &{}= 0 \\
\prodtime V & p(X_1,\,\ldots,\,X_n)        &{}= \prodtime V\,(\operatorname{body} p) \\
\prodtime V & V = \,f(X_1,\,\ldots,\,X_n)  &{}= \prodtime V\,(\operatorname{body} f) \\
\prodtime V & X_0(X_1,\,\ldots,\,X_n)      &{}= \mathit{time\_of\_call} \\
\prodtime V & m(X_1,\,\ldots,\,X_n)        &{}= \mathit{time\_of\_call} \\
\prodtime V & \mathit{foreign}(\ldots)     &{}= 0 \\
\prodtime V & G_\mathrm{head},\,G_\mathrm{tail}
\end{array}
\]
\end{document}

Best Answer

Related Solutions

[Tex/LaTex] Multiply defined labels using hyperref

[Tex/LaTex] Typesetting a pattern matching equation

Notes:

Code:

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