Adjusting the position of a box with tcolorbox

Question

I have already asked a similar question but I think that my request was unclear. I have created a box using tcolorbox and I want to adjust it in order to fit the length of my "normal" text (outside of item list). in the image below : I want the red box to be aligned on the red line on the left side and same on the right side.

\documentclass{article}

\usepackage{geometry}
\geometry{hmargin=1cm,vmargin=1.5cm}
\newcommand{\gap}{\vspace{0.5cm}} 
\usepackage{parskip}

\usepackage{enumitem}
\usepackage{pgf, tikz, adjustbox}
\usepackage{tcolorbox}

\begin{document}

\subsubsection{Conditions limites}

\begin{enumerate}[label=\Alph*)]
\item \textbf{En $i=1$}

\tcbset{colback=red!5!white,colframe=red!75!black,fonttitle=\bfseries, width = \linewidth-\parindent}
%
\begin{tcolorbox}[before upper={\parindent0em}]
\textbf{A retenir}
\[
h(x) = \left(h_N - h_{\infty} \right) e^{\frac{(L-x)}{\sqrt{2}}} \left[\cos \left(\frac{x}{\sqrt{2}}\right) \cos \left(\frac{L}{\sqrt{2}}\right)+ \sin \left(\frac{x}{\sqrt{2}}\right) \sin \left(\frac{L}{\sqrt{2}}\right) \right] + h_{\infty}
\]
\end{tcolorbox}
\end{enumerate}

\end{document}

A user advised me to specify the width by writing : width = \linewidth-\parindent} but it adjusts the "right side" only of my box. Now I want to do it for the left side but I don't know the procedure.

I was advised to use : \usepackage{parskip} but it didn't work as well.

Could someone help me please ?

Thank you,

Answer 1

The simplest, in my opinion, would be to end the enumerate environment before the \tcolorbox, and to use the resume* key when you want to continue the environment:

    \documentclass{article}

    \usepackage[showframe]{geometry}
    \geometry{hmargin=1cm,vmargin=1.5cm}
    \newcommand{\gap}{\vspace{0.5cm}}
    \usepackage{parskip}

    \usepackage{enumitem}
    \usepackage{pgf, tikz, adjustbox}
    \usepackage{tcolorbox}

    \begin{document}

    \subsubsection{Conditions limites}

    \begin{enumerate}[label=\Alph*)]
    \item \textbf{En $i=1$}
    \end{enumerate}]
    \tcbset{colback=red!5!white,colframe=red!75!black,fonttitle=\bfseries, width = \linewidth-\parindent}
    %
    \begin{tcolorbox}[before upper={\parindent0em}]
    \textbf{A retenir}
    \[
    h(x) = \left(h_N - h_{\infty} \right) e^{\frac{(L-x)}{\sqrt{2}}} \left[\cos \left(\frac{x}{\sqrt{2}}\right) \cos \left(\frac{L}{\sqrt{2}}\right)+ \sin \left(\frac{x}{\sqrt{2}}\right) \sin \left(\frac{L}{\sqrt{2}}\right) \right] + h_{\infty}
    \]
    \end{tcolorbox}

    \end{document} 

Answer 2

This is the expected behavior, since you are writing the box inside a list. However, if you insist on having a "full width" box, then you probably want to use the key spread sidewards. Since here your horizontal margin is even on both sides (hmargin=1cm), spread sidewards = 1cm will do the job.

\documentclass{article}

\usepackage{geometry}
\geometry{hmargin=1cm,vmargin=1.5cm}
\usepackage{parskip}

\usepackage{enumitem}
\usepackage{tcolorbox}

\begin{document}

\subsubsection{Conditions limites}

\begin{enumerate}[label=\Alph*)]
\item \textbf{En $i=1$}
\begin{tcolorbox}[colback=red!5!white, colframe=red!75!black, spread sidewards = -1cm]
    \textbf{A retenir}
    \[
    h(x) = \left(h_N - h_{\infty} \right) e^{\frac{(L-x)}{\sqrt{2}}} \left[\cos \left(\frac{x}{\sqrt{2}}\right) \cos \left(\frac{L}{\sqrt{2}}\right)+ \sin \left(\frac{x}{\sqrt{2}}\right) \sin \left(\frac{L}{\sqrt{2}}\right) \right] + h_{\infty}
    \]
    \end{tcolorbox}
\end{enumerate}

\end{document}