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From: Annada Behera <segfault@tilde.green>
Newsgroups: comp.text.tex
Subject: [LaTeX][PGF/TikZ] Undefined control sequence error for PGF
 intersections.
Date: Fri, 30 Aug 2024 13:29:14 +0530
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Consider this minimal working example. I have two functions, f(x) =3D x
and g(x) =3D x+sin(x). I want to draw them with PGF and at the intersection
points, I want put black dots. Here is the TikZ code,

    \documentclass{standalone}
    \usepackage{tikz, amsmath}
    \usetikzlibrary{intersections}
    \begin{document}\begin{tikzpicture}
       =20
        % Plots
        \draw[very thick, smooth, samples=3D20, domain=3D-6.28:6.28]=20
            [red,  name path=3Dline] (0,0) plot (\x, \x);
        \draw[very thick, smooth, samples=3D20, domain=3D-6.28:6.28]=20
            [blue, name path=3Dsine] (0,0) plot (\x, {\x + sin(\x r)});
       =20
        % Drawing the dots
        \fill[name intersections=3D{of=3Dline and sine, name=3Di, total=3D\=
t}, black]
            \foreach \s in {1,...,\t} {(i-\s) circle (2pt)};
       =20
    \end{tikzpicture}\end{document}

Now this code works as expected. But I also wanted to draw dashed lines fro=
m
the intersections to each axes.

    % Axes
    \draw [<->](-6.28, 0) -- (6.28, 0);
    \draw [<->](0, -6.28) -- (0, 6.28);

    % Mark intersection points and draw dashed lines
    \foreach \n in {1,...,\t} {
        \path ({i-\n}) coordinate (i\n); %    <--- Error Here
        \fill[black]  (i\n) circle (2pt);
        \draw[dashed] (i\n) -- (i\n |- 0,0);
        \draw[dashed] (i\n) -- (0,0 -| i\n);
    }

In this part, pdflatex (my distro is TeX Live 2024) throws an error what
I don't understand,

    ! Undefined control sequence.
    \UseTextAccent  ...p \@firstofone \let \@curr@enc=20
                                                      \cf@encoding \@use@te=
xt@en...
    l.28     }

What is undefined? I am pretty sure the name=3Di in \fill command populates
the namespace with i-1, 1-2 and 1-3, because \fill has drawn them. I
have even tried to help the parser with extra braces, {i-\n} and {i\n}
but that also doesn't help. Anybody know the reason why I get the error
and how to fix them?