制作半个椭圆虚线 - 圆柱体的着色和面积

Question

我在 tikz 中绘制椭圆时遇到了一些问题。有人能帮我（演示）如何绘制这样的图形吗？

我希望有人能引领我前行。

1. 我无法找到使某些区域变色的方法，例如在“a”和“b”之间。
2. 并且圆柱体位于“x_0”和“x”之间，带有斜线。
3. 我找不到让椭圆的一半像“a”那样虚线

我迄今为止的代码：

\documentclass[a4paper,10pt,twoside]{extarticle}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{graphicx}
\usepackage{xcolor}
\usepackage{tikz}
\usepackage{pgf}
\usepackage{amsmath,amssymb}
\usetikzlibrary{arrows,tikzmark}
\usetikzlibrary{calc,trees,positioning,arrows,chains,shapes.geometric,%
    decorations.pathreplacing,decorations.pathmorphing,shapes,%
    matrix,shapes.symbols}

\begin{document}
    
    \begin{center}
    \begin{minipage}[t]{0,45\textwidth}\centering
        %\vspace{1cm}
        \definecolor{cqcqcq}{rgb}{0.55,0.55,0.9}
        \definecolor{gitter}{rgb}{0.65,0.65,0.65}
        \centering
        \begin{tikzpicture}[line cap=round,line join=round,>=triangle 45,x=0.5cm,y=0.5cm, scale=1] 
            %\draw [color=gitter, xstep=0.5cm,ystep=0.5cm] (-5,-1) grid (5,10);  % Grid område
            \draw[->,color=black, line width=1pt] (-5,0) -- (15,0);    %X-akse
            %\draw[color=black] (-2,0) node[below] {\fontsize{7}{7}$\textbf{-2}$};  % -2 på xaksen
            \draw[color=black] (10,-0.4) node[below] {\fontsize{12}{12}$\textbf{b}$};  % b på xaksen
            \draw[color=black] (-3,-0.4) node[below] {\fontsize{12}{12}$\textbf{a}$};  % a på xaksen
            \draw[color=black] (15,0) node [anchor=west] {\fontsize{7}{7} \text{(1)}}; %Aksenanvn
            \draw[->,color=black, line width=1pt] (0,-10) -- (0,10);    %Y-akse
            \draw[color=black] (0,11.3) node [anchor=north] {\fontsize{7}{7} \text{(2)}}; % Aksenavn
            \clip(-5,-10) rectangle (15,10);
            \draw[smooth,samples=100,domain=-5:15, line width=1pt, color=blue] plot(\x,{0.002*(\x)^3-0.02*(\x)+0.25*(\x)+4});
            \draw[smooth,samples=100,domain=-3:10, line width=1pt, color=blue] plot(\x,{-0.002*(\x)^3+0.02*(\x)-0.25*(\x)-4});
            \draw[color=red,line width=1pt] (10,0) ellipse (0.5cm and 4.1cm); %grænse b
            \draw[color=red,line width=1pt] (-3,0) ellipse (0.5cm and 1.6cm); %Grænse a
            \draw (6,0) ellipse (0.5cm and 2.9cm);
            \draw (2,0) ellipse (0.5cm and 2.9cm);
            \draw (2,5.812) -- (6,5.812);
            \draw (2,-5.812) -- (6,-5.812);
            \draw[-,color=black,dashed, line width=1pt] (6,5.812) -- (6,0);
        \end{tikzpicture}
    \end{minipage}
\end{center}        
\end{document}

Answer 1

我建议不要明确设置字体大小，而是使用例如\large或变体。-不明确设置线宽，而是使用thick或变体。-不使用，color=black因为黑色是默认颜色。ellipse总是绘制一个完整的椭圆来绘制一部分，你可以使用arc。对于\fill一个区域，它需要是一条完全封闭的曲线。-首先用画一条封闭曲线\draw，然后用替换\draw。\fill这是一个开始：

\documentclass[tikz, border=1cm]{standalone}
\begin{document}
\begin{tikzpicture}
   \draw[->] (-2,0) -- (4,0) node[right] {(1)};
   \draw[->] (0,-3) -- (0,3) node[above] {(2)};
   \draw[color=red!80!black] (-1,0.4) arc [x radius=0.2, y radius=0.4, start angle=90, end angle=270];
   \draw[color=red!80!black, densely dotted] (-1,0.4) arc [x radius=0.2, y radius=0.4, start angle=90, end angle=-90];
   \draw (-1,-0.2) node {a};
   \draw[color=red!80!black] (3,0) ellipse [x radius=0.2, y radius=1];
   \draw (3,-0.2) node {b};
   \draw[blue, thick] (-1.4,0.3) to[out=10, in=190] (-1,0.4) to[out=10, in=210] (3,1) to[out=30, in=240] (4,1.5);
   \fill[red!50!yellow, opacity=0.5] (-1,-0.4) arc [x radius=0.2, y radius=0.4, start angle=-90, end angle=-270] to[out=10, in=210] (3,1) arc [x radius=0.2, y radius=1, start angle=90, end angle=-90] to[out=150, in=-10] cycle;
\end{tikzpicture}
\end{document}