draw line according to other angle

by lucky1928   Last Updated October 20, 2019 00:23 AM - source

In below example, how can I draw a line through C and satisfy formula (current D point should be changed)

\documentclass[border=3mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{calc,angles,quotes}

\begin{document}
    \begin{tikzpicture}[scale=2]
    \tikzset{dot/.style={circle,inner sep=1pt,fill,label={#1},name=#1},
    extended line/.style={shorten >=-#1,shorten <=-#1},
    extended line/.default=1cm
    }
    \pgfmathsetmacro\r{1}   
    \coordinate (O) at (-2,1);
    \path (O) -- ++(130:\r) coordinate (A)
          (O) -- ++(30:\r) coordinate (B)
          (O) -- ++(-90:\r) coordinate (C)
          ;
     \coordinate (D) at (0,0);
    \draw (O) circle (\r);
    \draw (A) -- (B) -- (C) -- cycle 
    pic["$\alpha$",draw,angle eccentricity=1.8,angle radius=6] {angle=C--A--B}
    pic["$\beta$",draw,angle eccentricity=1.8,angle radius=6] {angle=D--C--B};
    \draw[red,extended line=2cm] (C) -- (D);

    \foreach \x in {A,B,C,D,O} {
        \node[circle,fill,inner sep=0,minimum size=2pt,label=\x] at (\x) {};
    }
    \end{tikzpicture}
\end{document}

Output: enter image description here

Tags : tikz-pgf


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