如何在 Tikz 中填充由两个抛物线围成的区域？

Question

如何使用 Tikz 在两个抛物线之间填充？我尝试使用以下代码。但我无法填充该区域。

\documentclass{article}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[domain=0:2] 
 %\draw[very thin,color=gray] (-0.1,-1.1) grid (3.9,3.9);
 \draw[->] (-0.2,0) -- (4.2,0) node[right] {$x$}; 
 \draw[->] (0,-1.2) -- (0,4.2) node[above] {$y$};
 \draw[color=red]    plot (\x,\x^2)             node[right] {$y =x^2$}; 
\draw[color=blue]    plot (\x,\x^2/4)             node[right] {$y =x^2/4$}; 
 \end{tikzpicture}
 \end{document}

它产生：

Answer 1

像这样？

\documentclass{article}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[domain=0:2] 
 %\draw[very thin,color=gray] (-0.1,-1.1) grid (3.9,3.9);
 \draw[->] (-0.2,0) -- (4.2,0) node[right] {$x$}; 
 \draw[->] (0,-1.2) -- (0,4.2) node[above] {$y$};
 \fill[cyan] plot (\x,\x^2) -- plot[domain=2:0] (\x,\x^2/4);
 \draw[color=red]    plot (\x,\x^2)             node[right] {$y =x^2$}; 
 \draw[color=blue]    plot (\x,\x^2/4)             node[right] {$y =x^2/4$}; 
 \end{tikzpicture}
\end{document}

或者您也可以使用pgfplots。

\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{compat=1.16}
\usepgfplotslibrary{fillbetween}
\begin{document}
\begin{tikzpicture}
 \begin{axis}[domain=0:2,axis lines=middle,xlabel=$x$,ylabel=$y$,clip=false,
 xtick=\empty,ytick=\empty,unit vector ratio=1 1 1]
  \addplot[color=red,thick,name path=A] {x^2} node[right] {$y =x^2$};
  \addplot[color=blue,thick,name path=B] {x^2/4}  node[right] {$y =x^2/4$};    
  \addplot[cyan] fill between [of=A and B];
 \end{axis}
\end{tikzpicture}
\end{document}