How to center a text in landscape mode, at the exact center of the page?

Question

I need to write a text at the center of my page document in LaTeX.

I also need that text to be quite big (so I need a command for increasing the font dimension), together with the fact that this text will be a maths formula

For example, be this image the prototype of what I need:

Can someone help me with the code?

I already found a way to colorize the whole background with

\documentclass{article}
\usepackage{pagecolor}
\begin{document}
\pagecolor{green!5!}


\end{document}

But now I need the centering landscape way, plus fond increasing for a maths formula (hence not a pure text, and I know there are problems, usually, for that [or better: I also did have problems in the past with the font dimension related to the maths environment]).

Thanks in advance!

Answer 1

\documentclass[a4paper,landscape,fontsize=50pt]{scrartcl}
\usepackage{lmodern}
\usepackage{xcolor}
\pagestyle{empty}
\begin{document}
\color{red}
\[e^{i\pi} + 1 = 0\]
\end{document}

Or larger:

\documentclass[a4paper,landscape,fontsize=100pt,DIV=50]{scrartcl}
\usepackage{lmodern}
\usepackage{xcolor}
\pagestyle{empty}
\begin{document}
\color{red}
\[e^{i\pi} + 1 = 0\]
\end{document}

Answer 2

Here is the code for realizing such a thing.

\documentclass{article}
\usepackage{pagecolor}
\pagecolor{green!5!}
\usepackage{amsmath}
\usepackage{graphicx} % \scalebox
\usepackage{environ}
\usepackage{pdflscape}
\pagenumbering{gobble}% Remove page numbers (and reset to 1)
\NewEnviron{myequation}{%
\begin{equation*}
\scalebox{8.5}{$\BODY$}
\end{equation*}
}
\begin{document}
\begin{landscape}
\begin{center}
\vspace*{\fill}
\begin{myequation}
e^{\pi i} + 1 = 0
\end{myequation}
\vspace*{\fill}
\end{center}
\end{landscape}
\end{document}