Symbol for the length of a line/vector?

Question

How do I make a symbol for the length of a line or vector? I intend the following notation: |AD| is the length of AD. I can't find this symbol anywhere. (When I use shift+backslash in LaTeX, it gives a horizontal line).

For some reason the \cdot also doesn't seem to work, when I write it down like this:

&|AD| \cdot |BD|& = ...

So can anyone please tell me what I am doing wrong?

Did you try putting them in math mode $\| AB \|$ and & is a special character (in geeneral) column separator for tables and arrays. — percusse, Nov 07 '13 at 14:37
Have a look at this question and its answers How to look up a symbol or identify a math alphabet?. — Ludovic C., Nov 07 '13 at 14:40
shift+\ to me means | (a vertical bar). Do you get an horizontal line? — Sigur, Nov 07 '13 at 14:56
@LudovicC. The question was not about any symbol, but about delimiters instead. In that sense it is not a duplicate of the cited answer. — Michael Hoppe, Nov 07 '13 at 16:25
@MichaelHoppe Sure but it turns out that Detexify provides the right commands to get this delimiter. Plus I don't see really the difference between a symbol and a delimiter (in this context). — Ludovic C., Nov 07 '13 at 16:33
@LudovicC. The same “symbol”, e.g., |, may serve different purposes. — Michael Hoppe, Nov 07 '13 at 16:36

score 7 · Answer 1 · answered Nov 07 '13 at 14:55

Usually you use \[ \lvert AD \rvert \cdot \lvert BD \rvert \] relying on the amsmath package for this task. Often people wrap this into a macro called \abs or \norm like this:

\documentclass{article}
\usepackage{amsmath}

\newcommand{\norm}[1]{\lvert #1 \rvert}

\begin{document}
\[
    \norm{AD}\cdot\norm{BD}
\]
\[
    \lvert AD \rvert \cdot \lvert BD \rvert
\]
\end{document}

Przemysław Scherwentke · Answer 2 · 2018-11-06T08:46:14.310

3

edited Nov 06 '18 at 08:46

answered Nov 07 '13 at 15:15

Przemysław Scherwentke

37,268

Ow!! I've just discovered that the vertical bar in text mode produces an em dash line... lol – Sigur Nov 07 '13 at 15:36

Symbol for the length of a line/vector?

2 Answers2