[Tex/LaTex] Bold and italic at the same time (beamer)

Question

How can I make some text bold and italic at the same time (in the beamer class)? This example does not seem to work:

\documentclass{beamer}
\usetheme{Copenhagen}
\begin{document}
\frame{
    A number is \textbf{\textit{x}-smooth} if ...\\
    A number is \textbf{\emph{x}-smooth} if ...
}
\end{document}

Answer 1

Load a font that has the combination bf+it, e.g.

\usepackage{lmodern}

MWE

\documentclass{beamer}
\usetheme{Copenhagen}
\usepackage{lmodern}
\begin{document}
\frame{
    A number is \textbf{\textit{x}-smooth} if ...\\
    A number is \textbf{\emph{x}-smooth} if ...
}
\end{document}