1

This is my code, in \begin{align*} why am I getting an error saying I'm missing a $?

\begin{document}
%%
\begin{proof*}
\begin{align*}

1.; & (p \land q \rightarrow r, u \rightarrow \lnot r, u \land q) &&\aside{Premise}\
2.; & p \land q \rightarrow r   &&\aside{Premise} \
3.; & \equiv u \rightarrow \lnot r     &&\aside{Premise} \
4.; & \equiv u \land q                 &&\aside{Premise} \
5.; & \equiv u                         &&\aside{Specialization:3} \
6.; & \equiv \land r                   &&\aside{Modus Pones:2,4} \
7.; & \equiv \lnot (p \land q)         &&\aside{Modus Tollens:1,5} \
8.; & \equiv \lnot p \lor \lnot q      &&\aside{De Morgan's: ^} \
9.; & \equiv q                         &&\aside{Specialization:3}\
10.; & \equiv \lnot \lnot q             &&\aside{Double Negation:8}\
11.; & \equiv \lnot p                   &&\aside{Elimination:7,9}\


\end{align}
\end{proof}


%%
\end{document}
Leucippus
  • 1,636
Harper
  • 11
  • Please extend your code fragment to small but complete document begining with \documentclass and ending with \end{document}. What is \aside – Zarko Oct 06 '20 at 03:59
  • aside apparently just adds a comment, im doing it for a logic proof. what is code fragment? – Harper Oct 06 '20 at 04:03
  • Please, rather extend your code fragment to complete small document, which reproduce your error. If I put your align* into standard document container and define \aside command, I don't get any error ... – Zarko Oct 06 '20 at 04:09
  • 2
    Remove the blank lines. – Mico Oct 06 '20 at 04:13
  • thank you so much!!! how do i start a standard document container and how do i define aside? – Harper Oct 06 '20 at 04:16

2 Answers2

1

Welcome to TeX.SE!

To long for a comment ...

Since you not provide MWE, the following is based on usual use of the proof environment (see Theorems). In it is considered @Mico comment (removed are blank lines in align environment):

\documentclass{article}
\usepackage{amsmath,amsthm}
\newcommand\aside[1]{\text{#1}}

\begin{document}
    \begin{proof} % <---
\begin{align}
    1.\quad & (p \land q \to r, u \to \lnot r, u \land q) 
                        &&\aside{Premise}\
    2.\quad & p \land q \rightarrow r   &&\aside{Premise} \
    3.\quad & \equiv u \rightarrow \lnot r     &&\aside{Premise} \
    4.\quad & \equiv u \land q                 &&\aside{Premise} \
    5.\quad & \equiv u                         &&\aside{Specialization:3} \
    6.\quad & \equiv \land r                   &&\aside{Modus Pones:2,4} \
    7.\quad & \equiv \lnot (p \land q)         &&\aside{Modus Tollens:1,5} \
    8.\quad & \equiv \lnot p \lor \lnot q      &&\aside{De Morgan's: } \
    9.\quad & \equiv q                         &&\aside{Specialization:3}\
    10.\quad & \equiv \lnot \lnot q            &&\aside{Double Negation:8}\
    11.\quad & \equiv \lnot p                  &&\aside{Elimination:7,9}
        \qedhere
\end{align}%
    \end{proof} % <---
\end{document}

enter image description here

It gives no errors! Where and how you define ˙proof*`?

Zarko
  • 296,517
0

For some reason, align environment cannot process empty lines. So remove the empty lines and it should compile fine

Masum
  • 1,009