Why \texttt and \verb giving errors when using with LaTeX commands inside their input

Question

On latest version of MikTeX, following works:

\begin{align*}
\int sinxdx && \texttt{test line 1}\\
\int{sinx}dx && \texttt{test line 2}\\
\end{align*}

But the following gives error:

\begin{align*}
\int sinxdx && \texttt{\int sinxdx}\\
\int{sinx}dx && \texttt{\int{sinx}dx}\\
\end{align*}

The error:

Underfull \hbox (badness 10000) in paragraph at lines 94--102
[2] [3]
Overfull \hbox (40.0189pt too wide) detected at line 168
\OML/cmm/m/it/10.95 a=c \OMS/cmsy/m/n/10.95

When using \verb, the following is also giving a similar error:

\begin{align*}
\int sinxdx && \verb|test line 1|\\
\int{sinx}dx && \verb|test line 2|\\
\end{align*}

Answer 1

To get verbatim content inside the align* environments, my verbatimbox package can help.

\documentclass{article}
\usepackage{amsmath,verbatimbox}
\begin{document}
\begin{myverbbox}{\lineA}\int \sin x\,dx\end{myverbbox}
\begin{myverbbox}{\lineB}\int{\sin x}\,dx\end{myverbbox}
\begin{align*}
\int \sin x\,dx && \lineA\\
\int{\sin x}\,dx && \lineB\\
\end{align*}
\end{document}

For the other issue of \texttt, try \mathtt instead, which processes its argument in math mode.

---

ADDENDUM

The OP asks if this can be done without an additional package. Perhaps this would suffice:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align*}
\int \sin x\,dx && \texttt{\string\int~\string\sin~x\string\,dx}\\
\int{\sin x}\,dx && \texttt{\string\int\string{\string\sin~x\string}\string\,dx}
\end{align*}
\end{document}

Answer 2

You can't use \verb inside align*, just like in the argument to any other command; align is a special environment that reads its contents before starting typesetting and this has the consequence that \verb is not allowed. If you want to make examples of input and output, you can use array:

\documentclass{article}
\usepackage{array,booktabs}

\begin{document}

\[
\begin{array}{>{\displaystyle}ll}
\int \sin x \, dx & \verb|\int \sin x \, dx| \\
\addlinespace
\int \cos x \, dx & \verb|\int \cos x \, dx|
\end{array}
\]

\end{document}

Please, note the correct TeX notation; the spaces are optional (except the one between \sin and x.