2

I'd like to create a drawing that exhibit a way students could construct the tangent to a circle. This implies the drawing of a set square, and I'd want so see the remaining part of the circle in the hole of the set square. Here is where I am, but I'm stuck now. Any help would be very appreciated. If it's possible, I'd prefer a KISS solution ;-) !

\documentclass{article}
\usepackage{tikz}
\begin{document}
    \begin{tikzpicture}[scale=1.8]
        \node[fill, circle, minimum size=1pt, inner sep=2pt, label={[black, below left]:$O$}] (O) at (0,0) {} ;
        \node[fill, circle, minimum size=1pt, inner sep=2pt, label={[black, below right]:$A$}] (A) at (-60:1) {} ;
        \draw[very thick] (0,0) circle (1cm) ;
        \node at (-.8,.8) {$C$} ;
        \draw[very thick, gray, dashed] (O) -- (A) ;
        \node[shift={(30:4)}] (B) at (A.30) {} ;
        \node[shift={(-150:1)}] (C) at (A.-150) {} ;
        \draw[very thick, red] (B) node[above left] {$d$} -- (C) ;
        \draw[very thick, fill=gray, opacity=.5] (A) -- ++(120:.8) -- ++(0:1.6) -- (A) ;
        \draw[very thick, draw, fill=white, opacity=.5] (A) ++(75:.2) coordinate (D) -- ++(120:.43) -- ++(0:.86) -- (D) ;
    \end{tikzpicture}        
\end{document}
2

Argh ! I've found the answer, thanks to jake in "Highlighting part of TikZ figure".

Here is the code :

\documentclass{article}
\usepackage{tikz}
\begin{document}
    \begin{tikzpicture}[scale=1.8, remember picture]
        \node[fill, circle, minimum size=1pt, inner sep=2pt, label={[black, below left]:$O$}] (O) at (0,0) {} ;
        \node[fill, circle, minimum size=1pt, inner sep=2pt, label={[black, below right]:$A$}] (A) at (-60:1) {} ;
        \draw[very thick] (0,0) circle (1cm) ;
        \node at (-.8,.8) {$C$} ;
        \draw[very thick, gray, dashed, shorten >=-7mm, shorten <=-10mm] (O) -- (A) ;
        \node[shift={(30:4)}] (B) at (A.30) {} ;
        \node[shift={(-150:1)}] (C) at (A.-150) {} ;
        \draw[very thick, red] (B) node[above left] {$d$} -- (C) ;
    \end{tikzpicture}
    \begin{tikzpicture}[remember picture, overlay, even odd rule, scale=1.8]
        \filldraw[draw=black, fill=lightgray, opacity=1]
            (A) -- ++(120:.8) -- ++(0:1.6) -- (A) 
            (A) ++(75:.2) coordinate (D) -- ++(120:.43) -- ++(0:.86) -- (D) ;
    \end{tikzpicture}
\end{document}

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.