I need to write norm of sum, but the sum symbol is larger than tho norm symbol (||) and it doesn't look good. Is there any symbol for norm which will adjust its size?
\documentclass[12pt,a4paper]{article}
\begin{document}
\begin{equation}
||\left(\sum_{n=1}^N \bf P_{\rm n}\rm\right) ||^2 = \left(\sum_n \frac{E_n}{c}\right)^2 - \left(\sum_n \bf p_{\rm n}\rm \right)^2
\end{equation}
\end{document}
Best Answer
Either of the following methods should work:
You could load the
amsmath
package and define a\norm
macro as follows:and then write
in the equation of interest. Note that the round parentheses will be too big if you write
\left(
and\right)
; I recommend you write\biggl(
and\biggr)
instead.Your example code may therefore be written as
Some might say that the resulting norm "fences" in the example above are a bit too large and thus threaten to dominate visually the rest of the math stuff. (This happens, of course, because the macro uses
\left
and\right
directives to size the fences.) To fix this issue, you could load themathtools
package and insert the following instruction in the preamble:and use the
\norm
macro with an explicit size instruction (here:\bigg
, i.e., the same size as for the parentheses):