我想画这个图
我尝试过 Geogebra
\documentclass[12pt]{standalone}
\usepackage{fouriernc}
\usepackage{pgf,tikz}
\usepackage{mathrsfs}
\usetikzlibrary{arrows}
\pagestyle{empty}
\begin{document}
\begin{tikzpicture}[line cap=round,line join=round,>=triangle 45,x=1.0cm,y=1.0cm]
\draw[line width=1.2pt,->,color=black] (-2.5,0.) -- (2.5,0.);
\foreach \x in {-2.,-1.,1.,2.}
\draw[shift={(\x,0)},color=black] (0pt,2pt) -- (0pt,-2pt);
\draw[color=black] (2.3,0.031) node [anchor=south west] { $x$};
\draw[line width=1.2pt,->,color=black] (0.,-0.5) -- (0.,5.);
\foreach \y in {,1.,2.,3.,4.}
\draw[shift={(0,\y)},color=black] (2pt,0pt) -- (-2pt,0pt);
\draw[color=black] (0.025,4.835) node [anchor=west] {$y$};
\clip(-3.5,-0.5) rectangle (3.5,5.);
\draw[line width=1.2pt,smooth,samples=100,domain=-3.5:3.5] plot(\x,{(\x)^(2.0)});
\draw [domain=-3.5:3.5] plot(\x,{(--2.-3.*\x)/-1.});
\draw [fill=black] (1.,1.) circle (2.0pt);
\draw[color=black] (1.3,0.939) node {$A_0$};
\draw [fill=black] (2.,4.) circle (2.0pt);
\draw[color=black] (2.4,4) node {$A_n$};
\draw [fill=black] (0.667,0.) circle (2.0pt);
\draw[color=black] (1,-0.3) node {$M_n$};
\end{tikzpicture}
\end{document}
现在我想用pgfplots，我试过
\documentclass{standalone}
\usepackage{pgfplots}
\def\FunctionF(#1){(#1)^2}%
\begin{document}
\begin{tikzpicture}
\begin{axis}[
axis y line=center,
axis x line=middle,
axis on top=true,
xmin=-2.5,
xmax=2.5,
ymin=-1,
ymax=4.5,
height=5.0cm,
width=5.0cm,
grid,
xtick={-2,...,2},
ytick={-1,0,...,5},
]
\addplot [domain=-5:5, samples=50, mark=none, black] {\FunctionF(x)};
\end{axis}
\end{tikzpicture}
\end{document}
我得到了
如何绘制正割 A_nA_0M_n
答案1
使用pgfplots最新版本（1.13）：
\documentclass[border=3mm]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}
\usetikzlibrary{intersections}
\def\FunctionF(#1){(#1)^2}%
\begin{document}
\begin{tikzpicture}[
dot/.style = {red, opacity=0.5,
every node/.style={right=1pt, text=black, opacity=1,
fill=white, inner sep=1pt,
rounded corners=5pt, font=\footnotesize}
}
]
\begin{axis}[
axis y line=center,
axis x line=middle,
% axis on top=true,
xmin=-2.5,
xmax=2.8,
ymin=-1.5,
ymax=4.5,
height=5.0cm,
width=5.0cm,
grid,
tick label style={font=\scriptsize},
xtick={-2,...,2},
ytick={-1,0,...,5},
]
\addplot[domain=-5:5, samples=50, mark=none, black, smooth,
name path=A] {\FunctionF(x)};
\draw[red,name path=B] (0.5,-0.5) -- (2.16,4.5);
\path[name path=C] (0,0) -- (2,0);
\fill [name intersections={of=A and B, by={a,b}},dot]
(a) circle (1.2pt) node {$A_0$}
(b) circle (1.2pt) node {$A_n$};
\fill [name intersections={of=B and C, by=c},dot]
(c) circle (1.2pt) node {$M_n$};
\end{axis}
\end{tikzpicture}
\end{document}