Book: capital letter for chapter "number", normal letter for equation numbering in chapter

Question

The code below creates a chapter with capital I as chapter "number".

\documentclass{book}

\begin{document}

\setcounter{chapter}{8}%
\renewcommand{\thechapter}{\Alph{chapter}}%
\chapter{Introduction}

\begin{equation}
    e = mc^2
\end{equation}

\end{document}

And hence all equations in the chapter will be numbered as I.x (x being the number of the equation in the chapter).

I would prefer that in equations the I would however not be capitalized, e.g.:

I it possible to do this without changing the chapter numbering (I want to keep that capitalised).

Thanks!

Answer 1

It is as simple as

\renewcommand\theequation{\alph{chapter}.\arabic{equation}}

Normally this definition contains \thechapter but one can do what ever