我们如何创建这样的锻炼环境：

Question

我们如何才能创造这样的锻炼环境：

我试过：

\begin{tcolorbox}

\textbf{Câu 3}
Cho $x,y,z$ thỏa mãn $x^2+y^2+z^2=1.$ Chứng minh rằng
$$\dfrac{x^2}{1+2yz}+\dfrac{y^2}{1+2zx}+\dfrac{z^2}{1+2xy}\geqslant \dfrac{3}{5}$$

\end{tcolorbox}

但没有成功。我仍然无法在“Câu 3”周围放置一个彩色框

Answer 1

在下面的 MWE 中，我tcolorbox为左上角的文本使用了新定义的符号。符号包含在fontawesome5包中，可以通过访问\faToggleOn。文本周围的间距、框的高度、宽度和颜色当然可以根据您的需要进行调整。

为了摆脱外框的框架，我使用了boxrule=0pt, frame hidden，为了获得具有 90° 角而不是圆角的角，我添加了sharp corners。

\documentclass{article}
\usepackage{amssymb}
\usepackage{fontawesome5}
\usepackage[most]{tcolorbox}

\definecolor{mycolor}{RGB}{0,128,128}
\newtcbox{\mybox}{on line,
                  colback=mycolor,
                  fontupper=\bfseries\color{white},
                  boxrule=0pt,
                  arc=5pt, 
                  boxsep=0pt, 
                  left=2pt, 
                  right=2pt, 
                  top=5pt, 
                  bottom=5pt}
  
  
\begin{document}

\begin{tcolorbox}[boxrule=0pt, frame hidden, sharp corners]

\mybox{\faToggleOn\; Câu 3}
Cho $x,y,z$ thỏa mãn $x^2+y^2+z^2=1.$ Chứng minh rằng
\[\dfrac{x^2}{1+2yz}+\dfrac{y^2}{1+2zx}+\dfrac{z^2}{1+2xy}\geqslant \dfrac{3}{5}\]

\end{tcolorbox}

\end{document}

---

更新版本可自动对框内的框进行编号\section：

\documentclass{article}
\usepackage{amssymb}
\usepackage{fontawesome5}
\usepackage[most]{tcolorbox}

\definecolor{mycolor}{RGB}{0,128,128}
                  
                  
\newtcbtheorem[auto counter, number within=section,]{mycau}{\faToggleOn\; Câu}%
              {enhanced jigsaw,%
               sharp corners,%
               boxrule=0pt, 
               frame hidden,%
               colbacktitle= mycolor,
               boxed title style={boxrule=0pt, 
                                  frame hidden, 
                                  boxsep=0pt, 
                                  top=5pt, 
                                  bottom=5pt, 
                                  left=2pt, 
                                  right=2pt, 
                                  arc=5pt},
               attach boxed title to top left={xshift=0.5cm,yshift=-8mm},
               fonttitle=\color{white}\bfseries,%
               before upper=\hspace{2.5cm}
               }{th}

  
  
\begin{document}

\begin{mycau}{}{label}
Cho $x,y,z$ thỏa mãn $x^2+y^2+z^2=1.$ Chứng minh rằng
\[\frac{x^2}{1+2yz}+\frac{y^2}{1+2zx}+\frac{z^2}{1+2xy}\geqslant \frac{3}{5}\]
\end{mycau}

\end{document}

Answer 2

该xcolor包由包自动加载tcolorbox，提供了宏\colorbox和\textcolor；它们在这里派上用场了。

\documentclass{article}
\usepackage[vietnamese]{babel}
\usepackage{amsmath,amssymb,tcolorbox,fontawesome5}

% optional: load suitable text and math fonts:
\usepackage{unicode-math}
\setmainfont{Fira Sans}
\setmathfont{Fira Math Regular}[Scale=MatchLowercase]

\begin{document}
\begin{tcolorbox}[boxrule=0pt]
\colorbox{teal}{\textcolor{white}{\bfseries\faToggleOn\ Câu 3}}
Cho $x,y,z$ thỏa mãn $x^2+y^2+z^2=1.$ Chứng minh rằng
\[
\frac{x^2}{1+2yz}+\frac{y^2}{1+2zx}+\frac{z^2}{1+2xy} \geqslant \frac{3}{5}
\]
\end{tcolorbox}
\end{document}

Answer 3

受到@leandriis 和@Mico 的回答的启发，你可以将以下方法tcolorbox与以下锻炼包结合起来xsim：

\documentclass{article}
\usepackage[vietnamese]{babel}
\usepackage[T1]{fontenc}
\usepackage[margin=2cm]{geometry}
\usepackage{amssymb}
\usepackage{fontawesome}
\usepackage[most]{tcolorbox}
\usepackage{xsim}

\DeclareExerciseEnvironmentTemplate{custom}{%
  \begin{tcolorbox}[boxrule = 0pt]
  \tcbox[on line,colback=teal,colframe=teal,coltext=white,size=small]{%
    \faToggleOn\sffamily\bfseries\
    \XSIMmixedcase{\GetExerciseName}
    \GetExerciseProperty{counter}%
  }\quad
}{\hfill\textbf{Điện Biên}\end{tcolorbox}}

\xsimsetup{
  exercise/template = custom ,
  exercise/name = Câu
}
  
\begin{document}

\begin{exercise}
  Cho $x,y,z$ thỏa mãn $x^2+y^2+z^2=1$. Chứng minh rằng
  \[ \frac{x^2}{1+2yz}+\frac{y^2}{1+2zx}+\frac{z^2}{1+2xy} \geqslant \frac{3}{5} \]
\end{exercise}

\end{document}