3

I'm not entirely familiar with tikz but I want to create a drawing of a parabola, shaded (with the pattern, north west lines) and bounded. So far I've got this:

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{patterns}
\begin{document}
\begin{tikzpicture}

\draw [->] (-3,0)--(3,0) node [right] {$x$};
\draw [->] (0,-1)--(0,6) node [below left] {$y$};

\draw [ultra thick, black] (0,0) parabola(2,5) node{$\bullet$};
\draw [densely dotted] (-2,5) -- (2,5);
\draw [ultra thick, black] (0,0) parabola(-2,5) node{$\bullet$};


\draw [pattern=north west lines] (0,0) parabola (2,5);

\draw (-0.5,-0.3) node {$(0,0)$};
\draw (0,0) node{$\bullet$};

\end{tikzpicture}
\end{document}

And well, thats not exactly what I'm looking for...

And well, thats not exactly what I'm looking for as it leaves a lot of white space. If any suggestions could be made - I'm still fairly new and unexperienced, it would be much appreciated.

1
  • 1
    Welcome. // Can you please add a screenshot of your codes result to your question? (Unwanted white space etc.)
    – MS-SPO
    Jun 19, 2022 at 9:50

2 Answers 2

5

You can use parabola bend to also place the parabola vertex. A char \bullet is not guaranteed to be centered and it will depend on the font, so I use circle.

\documentclass[tikz, border=1cm]{standalone}
\usetikzlibrary{patterns}
\begin{document}
\begin{tikzpicture}
\draw[->] (-3,0)--(3,0) node [right] {$x$};
\draw[->] (0,-1)--(0,6) node [below left] {$y$};
\draw[ultra thick, black] (-2,5) parabola bend (0,0) (2,5);
\fill (-2,5) circle[radius=2pt] (0,0) circle[radius=2pt] (2,5) circle[radius=2pt];
\draw[densely dotted, thick] (-2,5) -- (2,5);
\draw[pattern=north west lines]  (-2,5) parabola bend (0,0) (2,5);
\draw (-0.5,-0.3) node {$(0,0)$};
\end{tikzpicture}
\end{document}

Aparabola with filling

3

A small variation of @hpekristiansen answer (+1) with use patterns.meta library:

\documentclass[tikz, border=3.141592]{standalone}
\usetikzlibrary{patterns.meta}

\begin{document}
    \begin{tikzpicture}[
dot/.style = {circle, fill, node contents={},
              inner sep=1.6pt, outer sep=0pt}
                        ]
% axis
\draw[->] (-3,0.0) -- (3,0) node [below left] {$x$};
\draw[->] (0,-0.5) -- (0,6) node [below left] {$y$};
% parabola 
\draw  [thick, 
        pattern={Lines[angle=45,distance={3pt},line width=0.2pt]},
                 pattern color=gray]
       (-2,5) parabola bend (0,0) (2,5);
\draw[densely dotted, semithick] 
    (-2,5) node[dot] -- (2,5) node[dot];
% coordinate origin
\path (0,0) node[below left] {(0,0)};
\end{tikzpicture}
\end{document}

enter image description here

Edit: removed superfluous nodes dot on parabola.

5
  • +1 I did not know node[dot] - I will try tor find it in the manual and read about it. Apparently it does not work with the parabola draw. Jun 19, 2022 at 12:27
  • Ok - I first now I see that you define the dot yourself. Strange, that it does not work in the parabola draw. Jun 19, 2022 at 12:32
  • 1
    @hpekristiansen, ups, Nodes dot should not be at parabola, but only at dashed line. Adding nodes to parabola make mess in drawings patterns. So i add them do on the top of dashed area. I defined dot simple to make the code shorter and more transparent.
    – Zarko
    Jun 19, 2022 at 12:52
  • You have dots both in parabola and in dashed line. To make it work in the parabola, you need fill=black in the dot definition otherwise the pattern will be applied instead of fill. Jun 19, 2022 at 12:54
  • @hpekristiansen, you are right. By mistake I forgot to delete dot on parabola (make some experiments, and after then apparently not clean-up final code). Thank you very much to spotted this.
    – Zarko
    Jun 19, 2022 at 13:01

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