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I am having trouble writing a term of an equation which is fractional where only the numerator is inside the absolute value symbol. The syntax I used is:
\frac{\abs{\lambda_f}}{8\pi^2}
But I keep getting an error saying, "Undefined control sequence". I think the nested curly braces is the problem but not sure how to fix it.
The documentation suggests \usepackage{steinmetz}
\documentclass{article}
\pagestyle{empty}
\usepackage{steinmetz}
\begin{document}
$\phase{abc}$
\end{document}
I have been using the code below using \DeclarePairedDelimiter from the mathtools package.
Since I don't think I have a case where I don't want this to scale based on the parameter, I make use of Swap definition of starred and non-starred command so that the normal use will automatically scale, and the starred version won't:
If you want it the other way around comment out the code between \makeatother...\makeatletter.
\documentclass{article}
\usepackage{mathtools}
\DeclarePairedDelimiter\abs{\lvert}{\rvert}%
\DeclarePairedDelimiter\norm{\lVert}{\rVert}%
% Swap the definition of \abs* and \norm*, so that \abs
% and \norm resizes the size of the brackets, and the
% starred version does not.
\makeatletter
\let\oldabs\abs
\def\abs{\@ifstar{\oldabs}{\oldabs*}}
%
\let\oldnorm\norm
\def\norm{\@ifstar{\oldnorm}{\oldnorm*}}
\makeatother
\newcommand*{\Value}{\frac{1}{2}x^2}%
\begin{document}
\[\abs{\Value} \quad \norm{\Value} \qquad\text{non-starred} \]
\[\abs*{\Value} \quad \norm*{\Value} \qquad\text{starred}\qquad\]
\end{document}
Best Answer
Make sure the
\absmacro is defined.