How to highlight borders of intersection and union? - TeX

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How to highlight borders of intersection and union?

tikz add tag

Topnush

Take this code:
```
    \documentclass{standalone}
    \usepackage{tikz}
    
    \begin{document}
    	\begin{tikzpicture}
    		
    		% Define the circles with transparency and borders
    		\begin{scope}[opacity=0.3]
    			\fill[blue] (0,0) circle (2);
    			\fill[red] (2,0) circle (2);
    		\end{scope}
    		
    		% Add black borders to circles
    		\draw[black, thin] (0,0) circle (2);
    		\draw[black, thin] (2,0) circle (2);
    		
    		% Label the sets (centered above circles)
    		\node at (0,2.3) {$A$};
    		\node at (2,2.3) {$B$};
    			
    	\end{tikzpicture}
    \end{document}
```

I would like to highlight the border of the intersection and separately the union.  How can I do that?
This will ultimately be two transitions in a beamer presentation.

Top Answer

samcarter

You can use `\clip` to highlight various sections of the border:

```
\documentclass{standalone}
\usepackage{tikz}

\begin{document}
  	\begin{tikzpicture}
  		
  		% Define the circles with transparency and borders
  		\begin{scope}[opacity=0.3]
  			\fill[blue] (0,0) circle (2);
  			\fill[red] (2,0) circle (2);
  		\end{scope}
  		
  		% Add black borders to circles
  		\draw[black, thin] (0,0) circle (2);
  		\draw[black, thin] (2,0) circle (2);
  		
  		% Label the sets (centered above circles)
  		\node at (0,2.3) {$A$};
  		\node at (2,2.3) {$B$};
      
      \begin{scope}
        \clip (-2.1,-2.1) rectangle (1,2.1);
        \draw[yellow, ultra thick] (0,0) circle (2);
      \end{scope}            
      
      \begin{scope}
        \clip (0,0) circle (2);
        \draw[green, ultra thick] (2,0) circle (2);
      \end{scope}
     
  	\end{tikzpicture}
\end{document}
```

![document-1.png](/image?hash=76499c478478d6dd6bd15b4d9d607df9c0bd4dddf0812b2dcc9e77161b683438)

1 Answer