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How do I represent the ordered pair representing a vector, without the usual open/close parentheses? My calculus textbook uses these:

component of vector

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2  
\langle a_1,a_2\rangle –  David Carlisle Apr 27 at 1:51
    
Welcome to TeX.SX! –  Heiko Oberdiek Apr 27 at 2:11
    
Thank you very much! –  user50608 Apr 27 at 2:17

2 Answers 2

\documentclass{article}
\usepackage{physics}
\usepackage{mathtools}
\DeclarePairedDelimiter{\opair}{\langle}{\rangle}
\begin{document}
  Using \verb|mathtools| and its \verb|DeclarePairedDelimiter| macro

  $\vb{a}=\opair{a,b}$

  Using \verb|physics| and its \verb|expval| macro

  $\vb{a}=\expval{a,b}$  or $\vb{a}=\ev{a,b}$
\end{document}

enter image description here

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?? Why not just use \documentclass{article}\begin{document}$\langle a,b\rangle$\end{document}? –  msh210 Apr 27 at 6:03
2  
@msh210 Well, in first place, I think it's easier to write something like \ev{a,b} than \langle a,b \rangle. In second place you can teach the command (whichever you use) to enlarge the delimiters \ev{a,\frac{b}{g}} instead of \biggl\langle a,\frac{b}{g} \biggr\rangle. And last, and most important in my opinion, if you choose a good (semantic) name, you will read your code much more easily and, moreover, if you decide to change the appearance of whatever construction you are using, you only have to redefine the macro. –  Manuel Apr 27 at 9:09
    
@msh210 Well Manuel has already given the reason and I meant the same. –  Harish Kumar Apr 27 at 12:51

It looks like you're asking about form, not how to get the angle brackets, is that right?

I really don't like those angle brackets, because they tend to get used to mean other things (typically, the inner product).

Really, in my opinion, the best way to treat vectors is just like matrices (column or row vectors).

\mathbf{a} = \begin{bmatrix}a_x & a_y\end{bmatrix}'$

or

\mathbf{a} = \begin{bmatrix}a_x\\a_y\end{bmatrix}

Alternatively, you can use element (unit) vectors

\mathbf{a} = a_x \hat{x} + a_y \hat{y}.

There are many ways of writing the unit elements. The strictly mathy way is to use $\mathbf{\mathup{e}}_x$, or $\hat\i$.

I prefer the column vectors. That way, dot products work out nicely as $\mathbf{a}'\mathbf{b}$. For example, (noting that the prime indicates transposition)

Output from example code.

Also, strictly speaking, the vectors should not be upright. They should be in bold italics. Upright symbols are reserved for mathematically defined quantities, such as pi, or e.

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