Math & Science ⇒ Letters in different Styles inside an Equation

[NELLLY]

Hi
when I typeset the following equation

Code: Select all

\begin{align*}
\displaystyle P(s'_{t+1}|s_t, a_t, o_{t+1})&=\frac{\rm
P(s'_{t+1},o_{t+1}|s_t,
a_t)}{\rm P(o_{t+1}|s_t, a_t)}\\
                             &=\frac{\rm P(o_{t+1}|s'_{t+1}, s_t,
                             a_t)}{\rm P(s'_{t+1}|s_t, a_t)}.
\end{align*}

The letters in the left side term are nice and in italic wherever the letters in the fractions of the right side are nor with the same style even if I use \displaystyle.
What should I do?

[localghost]

Please get used to always providing a complete example that is compilable for everybody as is. This increases your chance of getting help, especially when a problem becomes more complicated. You are not new to the forum so you should know that.

Regarding your problem, you can simply use the \dfrac command from amsmath to enable fractions in displayed math style.

Code: Select all

\documentclass[11pt]{article}
\usepackage{mathtools}   % loads »amsmath«

\begin{document}
  \begin{align*}
    P(s'_{t+1}|s_t, a_t, o_{t+1}) &= \dfrac{\mathrm{P}(s'_{t+1},o_{t+1}|s_t,a_t)}{\mathrm{P}(o_{t+1}|s_t, a_t)}\\
                                  &= \dfrac{\mathrm{P}(o_{t+1}|s'_{t+1},s_t,a_t)}{\mathrm{P}(s'_{t+1}|s_t, a_t)}.
  \end{align*}
\end{document}

Useful information about math typesetting can be found in the excellent »Math mode« document.

And by the way, you should not use obsolete LaTeX2.09 syntax for font styles in math mode. Use \mathrm{…} from LaTeX2e instead.


Thorsten

[NELLLY]

Hi
The problem still persist, the complete code is

Code: Select all

\documentclass [12pt]{report}
\usepackage[pdftex]{graphicx}
\usepackage[T1]{fontenc}
\usepackage{titlesec}
\usepackage{titletoc}
%\usepackage{fancychapters}
\usepackage[Lenny]{fncychap}
\usepackage{lettrine}
\usepackage{dropping}
\usepackage{float}
\usepackage{tabularx}
\usepackage{rotating}
\usepackage{amsmath,amssymb}
\usepackage{longtable}
\usepackage{booktabs}

\begin{document}

\begin{align*}
 P(s'_{t+1}|s_t, a_t, o_{t+1})&=\dfrac{\rm
P(s'_{t+1},o_{t+1}|s_t,
a_t)}{\rm P(o_{t+1}|s_t, a_t)}\\
&=\dfrac{\rm P(o_{t+1}|s'_{t+1}, s_t, a_t)}{\rm P(s'_{t+1}|s_t,
a_t)}.
\end{align*}
\end{document}

[Stefan Kottwitz]

Hi,

of course it persists, because you still use the obsolete \rm command. That's why the symbols are roman, not italic. Just remove \rm.

Stefan

[NELLLY]

This is perfect now, many thanks.