我提供了在笛卡尔平面上绘制三角形的代码。原点标记为 O，其他点标记为 A 和 B。三角形的高应绘制为从 O 到线段 AB 的虚线段，高线的底边标记为 P，高标记为 x。边长标记为 a、b 和 c。
我已绘制并标注了角度。其中一个角度未与三角形的一条边相交。代码有什么问题？“alpha”和“beta”的位置错误。为什么这些标签没有放在角度之外。（这些命令是从另一个文件中复制而来的，标签的位置恰好与此相符。）
\documentclass[10pt]{amsart}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsthm}
\usepackage{mathtools,array}
\usepackage{tikz}
\usetikzlibrary{calc}
\tikzset{
mydot/.style={
fill,
circle,
inner sep=1.5pt
}
}
\begin{document}
\begin{tikzpicture}[>=latex]
% the coordinates of the vertices
\coordinate (O) at (0,0);
\coordinate (A) at (122:4cm);
\coordinate (B) at (20:3cm);
% the axis
\draw[help lines,->] (-3.5,0) -- (2.5,0);
\draw[help lines,->] (0,-0.5) -- (0,5.5);
% the edges of the triangle
\draw (O) -- (A) -- (B) -- cycle;
% labelling the vertices
\node[mydot,label={left:$A$}] at (A) {};
\node[mydot,label={right:$B$}] at (B) {};
\node[mydot,label={below left:$O$}] at (O) {};
\draw ($(A)!(O)!(B)$);
% the arcs for the angles
\begin{scope}[gray]
\draw[->]
(0.75,0) +(0:0.5cm) arc [radius=1cm,start angle=0,end angle=20] node[midway,right] {$\beta$};
\draw[->]
(0.5,0) +(0:0.25cm) arc [radius=0.75cm,start angle=0,end angle=122] node[midway,above] {$\alpha$};
\end{scope}
\end{tikzpicture}
\end{document}
答案1
问题在于，对于该\beta角度，圆弧1.25cm从原点开始，但圆弧半径指定为1cm。
通过使用：
\draw[->] (0:1.25cm) arc (0:20:1.25cm) node[midway,right] {$\beta$};
圆弧将位于正确的位置：
\documentclass[tikz,border=5]{standalone}
\usetikzlibrary{calc}
\tikzset{
mydot/.style={
fill,
circle,
inner sep=1.5pt
}
}
\begin{document}
\begin{tikzpicture}[>=latex]
% the coordinates of the vertices
\coordinate (O) at (0,0);
\coordinate (A) at (122:4cm);
\coordinate (B) at (20:3cm);
% the axis
\draw[help lines,->] (-3.5,0) -- (2.5,0);
\draw[help lines,->] (0,-0.5) -- (0,5.5);
% the edges of the triangle
\draw (O) -- (A) -- (B) -- cycle;
% labelling the vertices
\node[mydot,label={left:$A$}] at (A) {};
\node[mydot,label={right:$B$}] at (B) {};
\node[mydot,label={below left:$O$}] at (O) {};
% the arcs for the angles
\begin{scope}[gray]
\draw[->] (0:1.25cm) arc (0: 20:1.25cm) node[midway,right] {$\beta$};
\draw[->] (0:0.75cm) arc (0:122:0.75cm) node[midway,above] {$\alpha$};
\end{scope}
\end{tikzpicture}
\end{document}
