auctex preview-latex does not take into account newcommands

Question

I have slightly complex symbols that I do not want to re-type in latex so I define \newcommands that abbreviate them. For example

\begin{document}
blah blah

\newcommand{\ds}[1]{\Delta\{#1\}}

\[
  \{x\} := \ds{a} + \ds{b_1} + \ds{c}
\]

blah blah
\end{document}

But when using preview-latex the \ds command is not recognized. Is there a way around this?

I am using auctex 12.3, emacs 26.3 and pdfTeX 3.14159265-2.6-1.40.21 (TeX Live 2020).

EDIT: It was pointed out that \newcommand{ds}{...} should be \newcommand{\ds}{...}. I edited the post to add the \ because that was a valid correction but it didn't solve the problem.

Answer 1

The syntax of \newcommand requires a backslash for the command to be defined: so not \newcommand{ds}{...}, but \newcommand{\ds}{...}

\begin{document}
  blah blah
 \newcommand{\ds}[1]{\Delta\{#1\}}
  %%         ^^^
 \[
 \{x\} := \ds{a} + \ds{b_1} + \ds{c}
 \]

 blah blah
 \end{document}