[Tex/LaTex] Poster quality math symbols/formulas presentation

Question

I would like to start/end a lecture by displaying a slide where a short symbol or equation is displayed prominently and fills up about half the screen, hopefully to focus the attention of students. For example it could be just $\int f(x)dx$ or just $\sin^2(x)+\cos^2(x)=1$. I like the equation to be framed (circular or rectangular) and use some contrasting background/foreground colors. Whatever brings the equation out of the page and has a gong quality to it would help. Any references to such files will be appreciated.

Edits:

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Answer 1

Since no one else has chimed in, I will convert my comment to an answer. As I had said, "most fonts are scalable, meaning that resolution scales to the available space."

The MWE below is a whole beamer slide, and can be seen to retain good resolution to very large font size.

\documentclass{beamer} 
\usepackage{xcolor,graphicx} 
\begin{document}
\begin{frame} 
\centering \fboxsep=5pt 
  \scalebox{6}{\colorbox{blue}{\color{white}$\int f(x)dx$}}\bigskip\par   
  \scalebox{2.8}{\colorbox{blue}{\color{white}$\sin^2(x)+\cos^2(x)=1$}}
  \end{frame} 
\end{document} 

Here is an alternative that does four (or five) things:

1. It makes the large equations in a roman, not sans serif, font, by renewing the \mathfamilydefault and

2. It set the integral in \displaystyle.

3. It uses an \fbox rather than \colorbox on the top equation (\fboxsep and \fboxrule are pertinent to the frame offset and thickness), and

4. It provides different color for frame vs. equation.

5. In frame 2, it allows specification of the equation height, rather than a scale factor.

Here is the MWE.

\documentclass{beamer} 
\usepackage{xcolor,graphicx,scalerel} 
\renewcommand\mathfamilydefault{\rmdefault}
\fboxsep=4pt \fboxrule 1pt
\begin{document}
\begin{frame}
\centering 
  \scalebox{5}{\color{blue!30!red}\fbox{\color{blue}$\displaystyle\int f(x)dx$}}\bigskip\par   
  \scalebox{2.8}{\colorbox{blue}{\color{white}$\sin^2(x)+\cos^2(x)=1$}} 
\end{frame}
\begin{frame}
\centering
  \scaleto{\color{blue!30!red}\fbox{\color{blue}$\displaystyle\int f(x)dx$}}{150pt}
  150pt high\bigskip\par   
  \scaleto{\colorbox{blue}{\color{white}$\sin^2(x)+\cos^2(x)=1$}}{50pt} 50 pt
\end{frame}
\end{document} 

Here is frame 1 with a scale factor applied

And here is frame 2 with a vertical height defined: