画一些圆圈和箭头

Question

我使用 latex 类beamer( \usetheme{Warsaw})。为了说明数学领域 C 源自领域 A 和领域 B，我需要在左右绘制两个圆圈（区域 A 和区域 B），两个箭头从这两个圆圈指向位于它们下方和中间的第三个圆圈（区域 C）。有什么想法如何绘制它吗？

Answer 1

灵感来自https://tex.stackexchange.com/a/283917/36296

\documentclass{beamer}
\usepackage{tikz}
\usetikzlibrary{arrows,positioning,trees} 

\tikzset{
    >=stealth',
    punkt/.style={
        circle,
        draw, 
        fill=blue!30,
        text centered},
    level 1/.style={sibling angle=120, level distance=1cm},
    edge from parent/.style= {draw=none},
}

\begin{document}
\begin{frame}
\begin{tikzpicture}

\coordinate (main) at (0,0) [clockwise from=270]
    child { node[punkt] (1) {A}}
    child { node[punkt] (2) {B}}
    child { node[punkt] (3) {C}}
;

\draw[->] (2) -- (1);
\draw[->] (3) -- (1);

\end{tikzpicture}
\end{frame}
\end{document}

Answer 2

另一个解决方案：

\documentclass{beamer}
\usepackage{tikz}
\usetikzlibrary{arrows,positioning}

\begin{document}
\begin{frame}
    \centering
\begin{tikzpicture}[
    node distance = 14.1 mm and 10 mm,
                > = stealth',
every node/.style = {circle, draw=blue!30!black, fill=blue!30,
                     minimum size=7mm}
                    ]
\node (b) {B};
\node (a) [below right=of b]    {A};
\node (c) [above right=of a]    {C};
%
\draw[->] (b) -- (a);
\draw[->] (c) -- (a);
\end{tikzpicture}
\end{frame}
\end{document}