使用 TikZ 包在两个特定点标记 x 轴？

Question

有没有办法在我的图中添加轴标签仅有的x = sqrt(2) 和 x = -sqrt(2)？

\documentclass{article}

\usepackage{tikz}

\begin{tikzpicture}
    \draw[<->] (-3,0) -- (3,0) node[right] {$x$};
    \draw[<->] (0,-3) -- (0,3) node[above] {$y$};
    \draw[scale=0.5,domain=-2.5:2.5,smooth,variable=\x,blue] plot ({\x},{\x*\x-2});
\end{tikzpicture}

Answer 1

欢迎光临！是的。

\documentclass{article}

\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[>=stealth]
    \draw[<->] (-3,0) -- (3,0) node[right] {$x$};
    \draw[<->] (0,-3) -- (0,3) node[above] {$y$};
    \draw[scale=0.5,domain=-2.5:2.5,smooth,variable=\x,blue] plot ({\x},{\x*\x-2});
    \draw foreach \X in {-1,1}
    { ({\X*sqrt(2)},0.1) -- ++ (0,-0.2) node[below]{$\ifnum\X<0 -\fi\sqrt{2}$}};
\end{tikzpicture}
\end{document}

或者，如果您想让标签接受比例变换。

\documentclass{article}

\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[>=stealth]
    \draw[<->] (-3,0) -- (3,0) node[right] {$x$};
    \draw[<->] (0,-3) -- (0,3) node[above] {$y$};
    \draw[scale=0.5,domain=-2.5:2.5,smooth,variable=\x,blue] plot ({\x},{\x*\x-2});
    \draw[xscale=0.5] foreach \X in {-1,1}
    { ({\X*sqrt(2)},0.1) -- ++ (0,-0.2) 
    \ifnum\X<0  [below left] \else  [below right] \fi node
    {$\ifnum\X<0 -\fi\sqrt{2}$}};
\end{tikzpicture}
\end{document}

Answer 2

这是一个解决方案pgfplots（尽管我无法删除 x 刻度）：

\documentclass[12pt]{article}
\usepackage{amsmath, amssymb}
\usepackage[usenames,dvipsnames,svgnames]{xcolor}
\usepackage{tikz}
\usetikzlibrary{positioning,calc}
\usepackage{pgfplots}
%\pgfplotsset{compat=1.12}

\begin{document}
\begin{tikzpicture} %y=x^-4

\begin{axis}[
axis lines=middle,
xticklabels={\empty},
yticklabels={\empty},
ymajorticks=false,
extra x ticks ={-sqrt(2),sqrt(2)},
extra x tick labels={$\sqrt{2}$,$-\sqrt{2}$},
xmin=-3,xmax=3,
ymin=-3,ymax=3,
extra x ticks={sqrt(2),-sqrt(2)},
xlabel=x,ylabel=y,
samples=200
]

\addplot[domain=-3:3,<->,>=latex,blue] {\x*\x-2};

\end{axis}

\end{tikzpicture}
\end{document}