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编辑（回复评论中的查询）

tag-icon • tag-icon tikz-pgf diagrams technical-drawing
编辑（回复评论中的查询）

如何绘制角度带有标签当这两条线不一定在同一个\draw调用中绘制时，这两条线之间如何？

我需要在 y 轴和摆绳之间画一个带有标签的角度 theta（见下图）。

欢迎对我的代码/图表提出其他建议/改进。

当前代码：

\documentclass[tikz,border=10pt]{standalone}
\usetikzlibrary{calc,patterns}
\begin{document}
\begin{tikzpicture}
\coordinate (origo) at (0,0);
\coordinate (pivot) at (1,5);

% draw axes
\fill[black] (origo) circle (0.05);
\draw[thick,gray,->] (origo) -- ++(4,0) node[black,right] {$x$};
\draw[thick,gray,->] (origo) -- ++(0,-4) node[black,below] {$y$};

% draw roof
\fill[pattern = north east lines] ($ (origo) + (-1,0) $) rectangle ($ (origo) + (1,0.5) $);
\draw[thick] ($ (origo) + (-1,0) $) -- ($ (origo) + (1,0) $);

\draw[thick] (origo) -- ++(300:3) coordinate (bob);
\fill (bob) circle (0.2);
\end{tikzpicture}
\end{document}

电流输出：

在此处输入图片描述

为了说明起见，我希望在我的图表中出现类似这样的内容：

在此处输入图片描述

答案1

您可以使用为此目的angles而定义的库。该库用于方便标记。picquotes

\documentclass[tikz,border=10pt]{standalone}
\usetikzlibrary{calc,patterns,angles,quotes}
\begin{document}
  \begin{tikzpicture}
    \coordinate (origo) at (0,0);
    \coordinate (pivot) at (1,5);

    % draw axes
    \fill[black] (origo) circle (0.05);
    \draw[thick,gray,->] (origo) -- ++(4,0) node[black,right] {$x$};
    \draw[thick,gray,->] (origo) -- ++(0,-4) node (mary) [black,below] {$y$};

    % draw roof
    \fill[pattern = north east lines] ($ (origo) + (-1,0) $) rectangle ($ (origo) + (1,0.5) $);
    \draw[thick] ($ (origo) + (-1,0) $) -- ($ (origo) + (1,0) $);

    \draw[thick] (origo) -- ++(300:3) coordinate (bob);
    \fill (bob) circle (0.2);

    \pic [draw, ->, "$\theta$", angle eccentricity=1.5] {angle = mary--origo--bob};
  \end{tikzpicture}
\end{document}

标记角度

如果想要带有双向箭头的红色角度，只需修改最后一行：

\pic [draw=red, <->, "$\theta$", angle eccentricity=1.5] {angle = mary--origo--bob};

修正标记角

编辑（回复评论中的查询）

要更改标签的颜色，只需设置text键：

\pic [draw=red, text=blue, <->, "$\theta$", angle eccentricity=1.5] {angle = mary--origo--bob};

修改后的修改标记角度

答案2

为了比较，这里有一个普通版本元帖子并附有一些解释性评论。

摆动的钟摆

prologues := 3;
outputtemplate := "%j%c.eps";

beginfig(1);

% first define the unit to use
u = 1cm;

% now define the paths and points
% next define the axes, the bob position, and the path of the pendulum
path xx, yy, pendulum; pair bob;
xx = (left -- 3 right) scaled u;
yy = (origin -- 4 down) scaled u;

theta = 24;
bob = 3 down scaled u rotated theta;
pendulum = origin -- bob;

% also define an angle mark, rotated to start on the yy axis and go as far as the pendulum
% this assumes theta is positive by the way
path angle_mark; angle_mark = fullcircle rotated 270 scaled 3/2u cutafter pendulum;

% now we can get on with drawing

% first do the striped fill for the roof area
path roof_area; roof_area = unitsquare shifted 1/2 left xscaled 2u yscaled 1/2u;
picture roof_fill;   
roof_fill = image(for x=-2u step 1/8u until 2u: draw (left--right) scaled 2u rotated 45 shifted (x,0); endfor);
clip roof_fill to roof_area;
draw roof_fill;

% now draw the axes in grey
drawarrow xx withcolor .5 white; label.rt (btex $x$ etex, point 1 of xx);
drawarrow yy withcolor .5 white; label.bot(btex $y$ etex, point 1 of yy);
% and the bottom of the roof area in black
draw subpath(0,1) of roof_area;
% draw the pendulum, the pivot at the origin, and the bob on the end of the pendulum
draw pendulum;
fill fullcircle scaled dotlabeldiam;
fill fullcircle scaled 1/3u shifted bob;

% now the angle mark - note it will lie on top of the axis and the pendulum
% if this bothers you, draw it first
ahlength := 2.5; 
drawarrow angle_mark withcolor .54 red;

% finally do the label, attached to the angle_mark
label(btex $\theta$ etex, point 1/2 of angle_mark + (1,-6)) withcolor .67 blue;

% and some optional go-faster stripes for the bob
for i=2 step 2 until 10:
  draw quartercircle scaled 1/3u rotated (135+theta-i) shifted (bob rotated -i) withcolor (i/10)*white;
endfor
endfig;
end.

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