matrices
I have this equation that doesnt fit the page
\documentclass[11pt]{article}
\usepackage{amsmath}
\begin{document}
\begin{equation*}
[a_{ii}]=[\phi]^T[A][\phi]=\begin{bmatrix}
-0.0829 + 0.2686i&0&0&0&0&0\\
0&-0.0829 - 0.2686i&0&0&0&0\\
0&0&-0.2040 + 2.5845i&0&0&0\\
0&0&0&-0.2040 - 2.5845i&0&0\\
0&0&0&0&3.2154&0\\
0&0&0&0&0&-3.0137
\end{bmatrix}
\end{equation*}
\end{document}
How can I correct it??
You may want to consider whether it's absolutely necessary to show up to 8 digits after the decimal point in order to convey the message you intend to send. If you can make do with, say, 4 digits after the decimal, you could use the siunitx package and its S column type to show the matrix in the form shown below. Note that it's not necessary to round and truncate the numbers by hand; siunitx will take of this job for you.
Incidentally, if the S column type is used, all numbers are aligned on the decimal points -- presumably a desirable thing, right? Note that with these modifications, it's not necessary at all to reduce the font size.
\documentclass{article}
\usepackage[margin=1in]{geometry} %
\usepackage{siunitx}
\sisetup{round-mode=places, % enable rounding
round-precision=4, % amounts of digits for rounding
table-format=-1.4} % default numeric format
\begin{document}
\begin{equation}
Q_{ij}=\left(
\begin{array}{*{4}{S}
S[table-format=3.4]
S
S[table-format=4.4]
S} % non-default values for "table-format" for columns 5 and 7
0.00301472 & -0.0961879 & -0.00897697 & 0.0389941 & -0.860642 & 0.0131329 & -4.73786 & -0.00552858\\
-0.028584 & 0.615003 & 0.111671 & -0.371008 & 4.94379 & -0.138279 & 20.3258 & 0.0512362\\
0.0132728 & -0.345125 & -0.0701132 & 0.115389 & -3.11777 & 0.102871 & -16.9949 & -0.0408223\\
2.91757 & 1.03545 & -5.16595 & 1.69976 & -22.1649 & 4.33453 & 120.513 & -1.35074\\
0.867566 & 2.92363 & -1.14174 & 3.4356 & -2.96193 & 1.91413 & -113.348 & -0.684269
\end{array}
\right)
\end{equation}
\end{document}
It was a bit hard to guess the intended layout from the markup fragment shown. It does not seem very wide unless you are setting in narrow columns. I set what I think was the intended expression on one line or two:
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\noindent X\dotfill X
\begin{equation*}
\begin{pmatrix}
0\\
0\\
0\\
0\\
0\\
0
\end{pmatrix} =
\begin{pmatrix}
0 & 0 & 0 & 0 & 0 & 0\\
0 & 0 & 0 & 0 & 0 & 0\\
0 & 0 & 0 & 0 & 0 & 0\\
0 & 0 & 0 & 0 & 0 & 0\\
0 & 0 & 0 & 0 & 0 & 0\\
0 & 0 & 0 & 0 & 0 & 0\\
0 & 0 & 0 & 0 & 0 & 0
\end{pmatrix}\begin{pmatrix}
0\\
0\\
0\\
0\\
0\\
0
\end{pmatrix}
+
\begin{pmatrix}
0\\
0\\
0\\
0\\
0\\
0
\end{pmatrix}
\end{equation*}
\begin{multline*}
\begin{pmatrix}
0\\
0\\
0\\
0\\
0\\
0
\end{pmatrix} =
\begin{pmatrix}
0 & 0 & 0 & 0 & 0 & 0\\
0 & 0 & 0 & 0 & 0 & 0\\
0 & 0 & 0 & 0 & 0 & 0\\
0 & 0 & 0 & 0 & 0 & 0\\
0 & 0 & 0 & 0 & 0 & 0\\
0 & 0 & 0 & 0 & 0 & 0\\
0 & 0 & 0 & 0 & 0 & 0
\end{pmatrix}\begin{pmatrix}
0\\
0\\
0\\
0\\
0\\
0
\end{pmatrix}\\
{}+
\begin{pmatrix}
0\\
0\\
0\\
0\\
0\\
0
\end{pmatrix}
\end{multline*}
\end{document}
Best Answer
Yet another possibility is negative space as column separator.