How to show latex commands in text mode

Question

Sorry for the basic question. What I want to do is to show the LaTeX command and, right after that, the output. But how can I show LaTeX formulas without obtaining errors for not using the math mode environment.

The problem is if I put the $...$, the formula appears and not the command. If I dont use the $...$ I get an error.

I have tried also to put inside a \text{}. No good either. Any suggestions? Thanks in advance.

Answer 1

You can use \verb as

\verb!$x^2 + y^2 = r^2$!

Or better use listings package

\lstinline[language={[LaTeX]TeX},basicstyle=\ttfamily]{$\sin^2\theta+\cos^2\theta=1$}

Full code:

\documentclass{article}
\usepackage{amsmath}
\usepackage{listings}

\begin{document}
Using \verb|\verb|:

\verb!$x^2 + y^2 = r^2$! \quad $\longrightarrow$ \quad $x^2 + y^2 = r^2$


Using \verb|listings|:

\lstinline[language={[LaTeX]TeX},basicstyle=\ttfamily]{$x^2 + y^2 = r^2$} \quad $\longrightarrow$ \quad $x^2 + y^2 = r^2$
\end{document}

Answer 2

Maybe this can meet your spectations

\documentclass{article}
\usepackage{xcolor}

\newcommand{\gfcb}[1]{%
    \fcolorbox{white}{gray!10!}{\quad\strut #1\quad}
    } % gfcb := gray fcolorbox
\newcommand{\cop}[1]{%
    \gfcb{\texttt{\detokenize{#1}}} 
    \ensuremath{\quad\longrightarrow\quad #1}
    } % cop := code output

\begin{document}

% Examples of usage

\cop{\ln x} \\

\cop{\sin x} \\

\cop{4\cdot a^n} \\

\cop{\sqrt{x^2+y^2}} \\

\cop{\displaystyle\int\cot^2 x\,dx} \\

\cop{\overline x=\dfrac{\sum_{i=1}^n x_i}{n}} \\

\cop{\displaystyle\lim_{\lVert \Delta x\rVert\to0}\sum_{k=1}^{n}f(c_i)\Delta x_i} \\

\cmdc{f(x)=\begin{cases}
x-4 & \text{if } x\leq 4 \\
x^3 & \text{if } x>4
\end{cases}} \\

\end{document}

I casually made it a couple of months ago when I had the same question while I was wondering how to display a command and its output for a LaTeX potential manual. And surfing TeX.SE I have just met this question.

The issue I got is that the code input can only be displayed in one line, so for big equations, that would not look good and would not fit the width of the page or paragraph.

UPDATE

In case you need to show large equations, you can use a tcolorbox that displays a code listing and its output.

\documentclass{report}
\usepackage{amsmath,amsthm,amssymb,latexsym}
\usepackage{tcolorbox.doc.s_main}
\usepackage{xcolor}
\usepackage{pgfplots}
    \pgfplotsset{compat=1.15}

\definecolor{midnightBlue}{RGB}{25,25,112}
\definecolor{webblue}{rgb}{0, 0, 0.5}

\begin{document}

\DeclareTCBListing{mybox}{ s O{} m }{%
colback=blue!10!,
colframe=webblue,
bicolor,
colframe=midnightBlue,
colbacklower=white,
after title={\hfill Output},
fonttitle=\bfseries,
IfBooleanTF={#1}
{text side listing}{listing side text},
title=#3,#2}

% Tcolobox with title
\begin{mybox}{Code}
$f(x)=\begin{cases}
x-4 & \text{if } x\leq 4 \\
x^3 & \text{if } x>4
\end{cases}$
\end{mybox}

% Tcolorbox without title
\begin{mybox}{}
$P(k):2(k+1)-3\leq2(k+1)-2$
\end{mybox}

\end{document}

Answer 3

  \begin{document}
  \begin{tabular}{cll}
   \begin{minipage}{3cm}
   \begin{verbatim}
      \ln x
   \end{verbatim} \end{minipage} & $\longrightarrow$ & 
  lnx\\
  \begin{minipage}{2cm}
  \begin{verbatim}
 4 \cdot a^n
  \end{verbatim} \end{minipage} & $\longrightarrow$ &
  $4 \cdot a^{n}$\\
 \begin{minipage}{2cm}
 \begin{verbatim}
  \sqrt{x^2+y^2}
 \end{verbatim} \end{minipage} & $\longrightarrow$ & 
 $\sqrt{x^2+y^2}$\\
  \end{tabular}

\end{document}

This has no packages. You have a lot of freedom to modify it. I am sure that you will enjoy it.