用tikz绘图，指定参数值，只能生成部分图形，全部改成数值后，可以生成正确图形。请指点。

用tikz画图就用tikz的方式来画图，你的需求大概是自定义一个图形，然后可以通过改变参数来改变图形，再tikz里可以把图形存储在pic中，然后通过修改键值的方式来完成，下面给了一个示例，需要更多参数仿照这个写就行了。 ```tex \documentclass[tikz, border=1cm]{standalone} \makeatletter \tikzset{ test inner x/.store in=\test@inner@x, test inner x=0.4, test inner y/.store in=\test@inner@y, test inner y=0.8, test outer x/.store in=\test@outer@x, test outer x=0.8, test outer y/.store in=\test@outer@y, test outer y=1.6, test width/.store in=\test@width, test width=3.8, test/.pic = { \draw[dotted] (0,0) ellipse ({\test@inner@x} and \test@inner@y); \draw (0,\test@outer@y) arc (90: 270: {\test@outer@x} and \test@outer@y); \draw [dotted](0,-\test@outer@y) arc (-90: 90: {\test@outer@x} and \test@outer@y); \draw (\test@width,0) ellipse ({\test@inner@x} and \test@inner@y); \draw (\test@width,0) ellipse ({\test@outer@x} and \test@outer@y); \draw (0,\test@outer@y) -- (\test@width,\test@outer@y); \draw (0,-\test@outer@y) -- (\test@width,-\test@outer@y); \draw [<->](0,-\test@outer@y-0.3) -- node[midway, below] {a}(\test@width,-\test@outer@y-0.3); \draw [red](\test@width,0) --node[midway, above] {$r$} (\test@width+\test@inner@x,0); \draw [red](\test@width,0) --node[midway, left] {$R$} (\test@width,-\test@inner@y); \filldraw[fill=teal,draw=black] (\test@width,0) circle (1pt); } } \makeatother \begin{document} \begin{tikzpicture} \pic at (0, 0) {test}; \pic[ test inner x = .2, test outer x = .4, test width = 5, ] at (0, -4) {test}; \end{tikzpicture} \end{document} ``` 

用大括号把 `and` 两边的命令括起来 ```tex \documentclass[tikz]{standalone} \begin{document} \begin{tikzpicture} \def\ra{0.4} %利用参数定义小，大椭圆，长度。 \def\rb{0.8} \def\Ra{0.8} \def\Rb{1.6} \def\a{3.8} \draw[dotted] (0,0) ellipse ({\ra} and {\rb}); \draw (0,\Rb) arc (90: 270: {\Ra} and {\Rb}); \draw [dotted](0,-\Rb) arc (-90: 90: {\Ra} and {\Rb}); \draw (3.8,0) ellipse (0.4 and 0.8); \draw (3.8,0) ellipse (0.8 and 1.6); \draw (0,\Rb) -- (\a,\Rb); \draw (0,-\Rb) -- (\a,-\Rb); \draw [<->](0,-\Rb-0.3) -- node[below] {a}(\a,-\Rb-0.3); \draw [red](\a,0) --node[above] {$r$} (\a+\ra,0); \draw [red](\a,0) --node[left] {$R$} (\a,-\rb); \filldraw[fill=teal,draw=black] (\a,0) circle (1pt); \end{tikzpicture} \end{document} ```

多谢指点。利用第一个回答，修正的代码： ```markdown \begin{tikzpicture} \def\ra{0.4} %利用参数定义小，大椭圆，长度。 \def\rb{0.8} \def\Ra{0.8} \def\Rb{1.6} \def\a{3.8} \draw[dotted] (0,0) ellipse ({\ra} and {\rb}); \draw (0,\Rb) arc (90: 270: {\Ra} and {\Rb}); \draw [dotted](0,-\Rb) arc (-90: 90: {\Ra} and {\Rb}); \draw (\a,0) ellipse ({\ra} and {\rb}); \draw (\a,0) ellipse ({\Ra} and {\Rb}); \draw (0,\Rb) -- (\a,\Rb); \draw (0,-\Rb) -- (\a,-\Rb); \draw [<->](0,-\Rb-0.3) -- node[below] {a}(\a,-\Rb-0.3); \draw [red](\a,0) --node[above] {$r$} (\a+\ra,0); \draw [red](\a,0) --node[left] {$R$} (\a,-\Rb); \filldraw[fill=teal,draw=black] (\a,0) circle (1pt); \end{tikzpicture} ``` [](https://wenda.latexstudio.net/data/attach/200604/2uo7G4r5.png)