我正在使用 LaTeX 绘制椭圆曲线tikzpicture
。我在图片上得到了图形,曲线定义为 -2,但我不知道为什么图形没有完成。
以下是代码:
\begin{tikzpicture}
\begin{axis}[
xmin=-4,
xmax=5,
ymin=-5,
ymax=5,
xlabel={$x$},
ylabel={$y$},
scale only axis,
axis lines=middle,
domain=-1.912931:3,
samples=200,
smooth,
clip=false,
% use same unit vectors on the axis
axis equal image=true,
]
\addplot[blue] {sqrt(x^3-3*x+5)} node[right] {$E$};
\addplot[blue] {-sqrt(x^3-3*x+5)};
\coordinate[label={10:$P$}] (P) at (axis cs:-1,2.64);
\end{axis}
\end{tikzpicture}
答案1
您选择了 的域-1.912931:3
。使用更正后的域,它(几乎)可以工作(来自https://www.wolframalpha.com/input/?i=abs(sqrt(x^3-3*x%2B5))+%3D+0
)。
\documentclass{article}
\usepackage{pgfplots}
\begin{document}
\begin{tikzpicture}
\begin{axis}[
xmin=-4,
xmax=5,
ymin=-5,
ymax=5,
xlabel={$x$},
ylabel={$y$},
scale only axis,
axis lines=middle,
domain=-2.279018:3,
samples=201,
smooth,
clip=false,
% use same unit vectors on the axis
axis equal image=true,
]
\addplot[blue] {sqrt(x^3-3*x+5)} node[right] {$E$};
\addplot[blue] {-sqrt(x^3-3*x+5)};
\coordinate[label={10:$P$}] (P) at (axis cs:-1,2.64);
\end{axis}
\end{tikzpicture}
\end{document}
答案2
仅说明你在做什么:
蓝线属于你的 mwe,红线位于未定义的域:
\documentclass[margin=3mm]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.15}
\begin{document}
\begin{tikzpicture}
\begin{axis}[
xmin=-3, xmax=5,
ymin=-5, ymax=5,
xlabel={$x$},
ylabel={$y$},
scale only axis,
axis lines=middle,
clip=false,
domain=-2.279:3, % <-- as sugested by TeXnician
samples=101,
% use same unit vectors on the axis
axis equal image=true,
]
\addplot[red,domain=-2.279:-2] {sqrt(x^3-3*x+5)};
\addplot[blue,domain=-2:3] {sqrt(x^3-3*x+5)} node[right] {$E$};
\addplot[red,domain=-2.279:-2] {-sqrt(x^3-3*x+5)};
\addplot[blue,domain=-2:3] {-sqrt(x^3-3*x+5)};
\coordinate[pin=120:{$(-2.279,0)$}] (aux) at (-2.279,0);
\coordinate[pin=120:{$(-2,\sqrt{3})$}] (aux) at (-2,1.73205);
\draw[densely dashed, very thin] (-2,-5) -- (-2,5);
\coordinate[label={10:$P$}] (P) at (-1,2.64);
\end{axis}
\end{tikzpicture}
\end{document}