我准备用tikz画这样的一个图  图中`A`和`B`区域打算用不同的颜色区分，可是该如何用`\fill`(或其他命令)命令实现呢？ 目前能做到的代码如下 ```tex \documentclass[UTF8]{standalone} \usepackage{amsmath,fourier,ctex,tikz} \begin{document} \begin{tikzpicture}[domain=-0.3:3] \draw[-latex] (-0.3,0) node[left=-3pt,below=-2pt] {$O$} -- (2,0) node[below] {$x$}; \draw[-latex] (0,-0.3) -- (0,2) node[left] {$y$}; \draw[domain=0:1.2] plot (\x,{0.5*\x^2}) node[right] {$y = x^{2}$}; \draw[domain=0:0.9] plot (\x,{2*\x^2}) node[right] {$y = 2x^{2}$}; \draw[domain=0:0.62] plot (\x,{3.5*\x^2}) node[above] {$L$}; \draw[dashed] (0.8,2*0.8^2) -- (0,2*0.8^2); \draw[dashed] (0.8,2*0.8^2) -- (0.8,0); \fill[domain=0:0.8,fill=gray] (0,0) plot (\x,{0.5*\x^2}) -- (0.8,2*0.8^2) plot (\x,{2*\x^2}); \end{tikzpicture} \end{document} ``` 不知道怎么才能将`y = 2x^{2}`设置为阴影的边界