Math & Science ⇒ left bracket only

[Philosophaie]

If you have a table using tabular. You have to use the brackets \left and \right as a pair. What if I want to input a left bracket only what are my choices?

Plus also how do you insert a space when there is no current \begin s except for \begin{document} where \\ does not work?

[cgnieder]

You can either explicitly size the delimiter to the size you want using \big, \Big, bigg or Bigg (depending on the size you want). Maybe better: for a left delimiter \bigl, \Bigl, biggl or Biggl and for a right delimiter \bigr, \Bigr, biggr or Biggr.

For a \left/\right pair there is also the empty delimiter .:

Code: Select all

\documentclass{article}
\usepackage{amsmath}
\begin{document}

\begin{align}
  \biggl(\frac{1}{2} \\
  x^2
\end{align}

\begin{align}
  \left(\frac{1}{2}\right. \\
  x^2
\end{align}

\end{document}

As for your question on spaces: I admit I didn't really understand what you mean.

Regards

[Johannes_B]

Code: Select all

\documentclass{article}
\usepackage{showframe}
\begin{document}
\vspace*{2cm}
\rule{.5\textwidth}{4pt}
\end{document}

Never (i.e. never) use a double backslash to create vertical space. Never ever (except you know why you are allowed to do it in a certain case).