把圆圈放在球体旁边

Question

我试图将圆圈与球体并排放置，这是我的尝试

\documentclass{article}
\usepackage{lipsum}
\usepackage{graphicx}
\usepackage{caption}

\begin{document}

\begin{figure}[h]

    \centering
    \begin{minipage}
    \centering
    \begin{tikzpicture}         
        \draw[fill=none](0,0) circle (1.0) node [black,yshift=-1.5cm] {2-bola};
        \draw[fill=black](0,0) circle (1 pt) node [above] {\tiny a};
        \draw[](0,0) -- (1,0) node [midway,above] {$\scriptstyle r$};
        
        \draw (-1,0) arc (180:360:1cm and 0.5cm);
        \draw[dashed] (-1,0) arc (180:0:1cm and 0.5cm);
        \draw (0,1) arc (90:270:0.5cm and 1cm);
        \draw[dashed] (0,1) arc (90:-90:0.5cm and 1cm);
        \draw (0,0) circle (1cm);
        \shade[ball color=blue!10!white,opacity=0.20] (0,0) circle (1cm);
     \end{tikzpicture}

    \end{minipage}

   \hfill

     \begin{minipage}

        \centering

        \begin{tikzpicture} 
            
            \draw[fill=none](0,0) circle (1.0) node [black,yshift=-1.5cm] {2-bola};
            \draw[fill=black](0,0) circle (1 pt) node [above] {\tiny a};
            \draw[](0,0) -- (1,0) node [midway,above] {$\scriptstyle r$};
     \end{tikzpicture}
        
     \end{minipage}
\end{figure}
\end{document}

我得到了这个和错误......

错误是什么？

Answer 1

删除minipage图片之间的 s 和空行后，我得到以下结果：

\documentclass{article}
\usepackage{tikz}
\usepackage{lipsum}
\usepackage{graphicx}
\usepackage{caption}

\begin{document}
    \begin{figure}[ht]
\centering
\begin{tikzpicture}
    \draw[fill=none](0,0) circle (1.0) node [black,yshift=-1.5cm] {2-bola};
    \draw[fill=black](0,0) circle (1 pt) node [above] {\tiny a};
    \draw[](0,0) -- (1,0) node [midway,above] {$\scriptstyle r$};

    \draw (-1,0) arc (180:360:1cm and 0.5cm);
    \draw[dashed] (-1,0) arc (180:0:1cm and 0.5cm);
    \draw (0,1) arc (90:270:0.5cm and 1cm);
    \draw[dashed] (0,1) arc (90:-90:0.5cm and 1cm);
    \draw (0,0) circle (1cm);
    \shade[ball color=blue!10!white,opacity=0.20] (0,0) circle (1cm);
\end{tikzpicture}
\hfil
\begin{tikzpicture}
    \draw[fill=none](0,0) circle (1.0) node [black,yshift=-1.5cm] {2-bola};
    \draw[fill=black](0,0) circle (1 pt) node [above] {\tiny a};
    \draw[](0,0) -- (1,0) node [midway,above] {$\scriptstyle r$};
\end{tikzpicture}
    \end{figure}
\end{document}

附录： 但是，您也可以按照以下方式绘制图像：

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{positioning,
                quotes,
                shadings}
\tikzset{
    node distance = 2mm and 12mm,
      C/.style = {circle, draw, minimum size=#1, inner sep=0pt},
    dot/.style = {circle, fill, inner sep=1.2pt, node contents={}},
every edge quotes/.style = {auto, font=\footnotesize, text=black},
      S/.style = {ball color=blue!30,opacity=0.20},
        }

\begin{document}
    \begin{center}
\begin{tikzpicture}
\def\R{1cm}
\shade[S]   (0,0) circle[radius=\R];
    \node (n1)  [C=2*\R, label=below:2-bola] {};
    \node (n2)  [dot, label=$a$] {};
\draw   (n1.west)  arc (180:360:1cm and 0.5cm)
        (n1.north) arc (90:270:0.5cm and 1cm);
\draw[dashed] 
        (n1.west)  arc (180:0:1cm and 0.5cm)
        (n1.north) arc (90:-90:0.5cm and 1cm);
\draw   (n2) to [pos=0.6,"$r$"] (n1.east);

\begin{scope}[xshift=44mm]
\shade[S]   (0,0) circle[radius=\R];
    \node (n1)  [C=2*\R, label=below:2-bola] {};
    \node (n2)  [dot, label=$a$] {};
\draw   (n2) to [pos=0.6,"$r$"] (n1.east);
    \end{scope}
\end{tikzpicture}
    \end{center}
\end{document}

结果与以前非常相似：

Answer 2

\documentclass{article}
\usepackage{tikz}
\usepackage{lipsum}
\usepackage{graphicx}
\usepackage{caption}



\begin{document}

\begin{center}
\begin{tikzpicture}
 \draw[fill=none](0,0) circle (1.0) node [black,yshift=-1.5cm] {2-bola};
 \draw[fill=black](0,0) circle (1 pt) node [above] {\tiny a};
 \draw[](0,0) -- (1,0) node [midway,above] {$\scriptstyle r$};        
 \draw (-1,0) arc (180:360:1cm and 0.5cm);
 \draw[dashed] (-1,0) arc (180:0:1cm and 0.5cm);
 \draw (0,1) arc (90:270:0.5cm and 1cm);
 \draw[dashed] (0,1) arc (90:-90:0.5cm and 1cm);
 \draw (0,0) circle (1cm);
 \shade[ball color=blue!10!white,opacity=0.20] (0,0) circle (1cm);
\end{tikzpicture}
\hspace{1cm}
\begin{tikzpicture}
 \draw[fill=none](0,0) circle (1.0) node [black,yshift=-1.5cm] {2-bola};
 \draw[fill=black](0,0) circle (1 pt) node [above] {\tiny a};
 \draw[](0,0) -- (1,0) node [midway,above] {$\scriptstyle r$};
\end{tikzpicture}

\end{center}

\end{document}