# Why is my beamer presentation failing to compile when I include letters in my math?

Forgive me I am new to LaTex. I have a presentation that I would like to do in Beamer, but it fails to compile when I include letters in my math statements.

For example, the following will compile,

\documentclass{beamer}

\usepackage{amsmath}

\begin{document}

\title{Midterm Presentation of Doom}

\frame{\frametitle{Example}

$1 + 1$

$\lambda$

}

\end{document}


However, the following will NOT complile,

\documentclass{beamer}

\usepackage{amsmath}

\begin{document}

\title{Midterm Presentation of Doom}

\frame{\frametitle{Example}

$1 + 1 = a$

$\lambda * b$

}

\end{document}


The error that I get are

  Font shape OT1/cmss/m/n' in size <4> not available(Font) size <5> substituted


I am using TeXstudio 2.6.6 + MikTex 2.9, if this matters.

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That is not an error, it's just an informational message – David Carlisle Apr 11 '14 at 21:47
Prefer the syntax \begin{frame}\frametitle{Title}<BODY>\end{frame} – egreg Apr 11 '14 at 22:15

Both your example codes compile with no errors, and both of them produce the warning messages

LaTeX Font Warning: Font shape OT1/cmss/m/n' in size <4> not available size <5>
substituted on input line 15.

LaTeX Font Warning: Size substitutions with differences up to 1.0pt have occurred.


As David has pointed out in his comment, those are not errors but just warning messages informing you that some font sizes (4pt, in this case) were not available in the current font used, so LaTeX used a different back-up size (5pt) instead.

The warnings come from the fact that beamer defines (the definitions are in beamerbasefont.sty) and uses some non-standard font sizes \Tiny and \TINY:

\newcommand\Tiny{\@setfontsize\Tiny{4}{5}}
\newcommand\TINY{\@setfontsize\Tiny{3}{4}}


which are not available in the default CM fonts. You can prevent the warning in a number of ways:

1. By loading the fix-cm package if you want to stick to CM fonts.

2. By loading another font with arbitrary scalable sizes, such as lmodern (and using the professionalfonts font theme for beamer):

\usepackage{lmodern}
\usefonttheme{professionalfonts}

3. If none of the above is a valid option, as a last resource you can \let the problematic size to a familiar one, by adding to the preamble

\let\Tiny\tiny


By the way, there's no need to explicitly load amsmath with beamer, since the class internally loads it.

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Thank your for your help. Using either \usepackage{lmodern} or \usefonttheme{professionalfonts} allows my presentation to compile with out error or warnings. – Jeremy Apr 12 '14 at 15:09