一个标题中可以有多个换行符吗？

Question

也许这是对你的问题更好的解决方案？假设，你想将这些仅仅相似的三角形作为一个浮点数呈现，包含三个子图。

我将标题字体大小的定义放入序言中，以便让一个定义以相同的方式作用于文档中的所有标题。

您必须加载包subcaption。在某些情况下，subcaption不起作用，例如 Springer 期刊等。在这种情况下，您必须使用包subfigure。

编辑：根据评论，我改变了我的 MWE。

我添加了缺失的节点。
我添加了缺失的角度，并标注为$\theta
为了避免不必要的输入，我创建了一个新命令\triang（\triangle已定义），并采用（截至目前） 3 个参数来标记三行。

我试图画出角度，$\theta但只是猜测了结束角度。看来，30° 也应该满足。为了穿过斜边，我增加了角度以end angle确保万无一失，并剪掉了三角形外部的所有内容。

更好的方法是，通过定义第四个参数来定义一个变量三角形，表示所需的角度。也许我可以这样做，稍后会添加该示例。

到目前为止，这是我的 MWE：

\documentclass{report}
\usepackage[a4paper,width=150mm,top=25mm,left=15mm,bottom=25mm,right=15mm,bindingoffset=10mm]{geometry}
\usepackage[justification=centering]{caption}
\usepackage{subcaption}
\usepackage{tikz}
\usepackage{tikz-3dplot}
\usetikzlibrary{shapes.geometric, decorations.pathreplacing, matrix,
  angles, quotes, arrows, arrows.meta, datavisualization} 
\usepackage{pgfplots}


\newcommand\captionlinebreak{\ifsinglelinecaption\space\else\\\fi}
%% better to be defined in the preamble?
\captionsetup{font=footnotesize}%

%% Te speed up the programming: define this command, to draw a
%% triangle.  The arguemtns denote:
%%      #1: label of the AC-line (hypothenuse)
%%      #2: label of the CB-line (opposite line, Gegenkathethe)
%%      #3: label of the AB-line (adjacent line, Ankathethe)
\newcommand{\triang}[3]{%
  \begin{tikzpicture}[scale=1.0%
    % ,cap=round
    % ,>=latex
    ]%
    %% Define the ccordinates, where to put the corners of the
    %% triangle.  These were given by the OP.  I'd suggest to put
    %% Point A on the origin, which is (0,0)
    \coordinate [label=left:$A$] (A) at (-1.5cm,-1.cm);%
    \coordinate [label=above:$B$] (B) at (1.5cm,1.0cm);%
    \coordinate [label=right:$C$] (C) at (1.5cm,-1.0cm);%
    %% coordinates of the angle Theta
    \coordinate [label=right:$\theta$] (Theta) at (-1cm, -0.8cm);%
    %% draw the trinangle
    \draw (A) -- node[above, rotate=35] {#1} (B) -- node[right] {#2} (C) --%
    node[below] {#3} (A);%
    %% draw the rectangular corner
    \draw (1.25cm,-1.0cm) rectangle (1.5cm,-0.75cm);%
    %% Now draw the angle arc.  To be sure, that the arc will join the
    %% hypothenuse, lets make the end angle somewhat bigger, in order
    %% to protrude the hypothenuse.  Use clip to cut it in the
    %% hypothenuse.
    \clip (A) -- (B) -- (C) -- (A);%
    \draw (-1.1cm, -1cm) arc[start angle=0, end angle=40, radius=4mm];%
  \end{tikzpicture}%
}


\begin{document}
\begin{figure}
  \centering
  \begin{subfigure}[b]{0.3\linewidth}
    \centering
    \triang{$c$}{$a$}{$\sqrt{c^{2}-a^{2}}$}
    \caption{$u=a\sin\theta$}
  \end{subfigure}%
  \begin{subfigure}[b]{0.3\linewidth}
    \centering
    \triang{$\sqrt{a^2 + b^2}$}{$a$}{$b$}
    \caption{$u=\sqrt{a^2 + u^2} \sin \theta$}
  \end{subfigure}%
  \begin{subfigure}[b]{0.3\linewidth}
    \centering
    \triang{$c$}{$\sqrt{c^2 - b^2}$}{$b$}
    \caption{$a=u \cos \theta$}
  \end{subfigure}
  %% Now the main caption.  Of course, captions may have more than one line.
  \caption{Triangle calculations by means of trigonometric functions.\\
  To utilize trigonometric functions, you'll have to apply them on a
  triangle, which has a right angle.  There are the functions Sinus,
  Cosinus and Tanges.  Sinus is defined as the fraction of the length
  of the opposite site to the length of the hypothenuse.}
  \label{fig:triangle}
\end{figure}
\end{document}

输出如下所示：

因此，这是我的第二次尝试。我进行了以下更改：

我重新设计了宏\triang，使其基于给定的角度。现在角度在第一个参数中定义，即 #1。
我将点“A”定义为原点(0,0)。
我切换到极坐标，以点“B”为端点绘制斜边。现在显示\coordinate [label=above:$B$] (B) at (#1:\@triaglen);为其中#1表示可变角度和\@triaglen斜边的定义长度。
为了使三角形的路径正常工作，TikZ 必须根据给定的角度计算线 BC 与斜边“AB”以及 x 轴本身的交点。定义现在为\coordinate [label=right:$C$] (C) at (#1:\@triaglen |- 0,0);。请注意坐标。它写为一组坐标和标记|-。看看TikZ-手册在第38页。
为了调整角度 Theta 标签的位置，我还更改了它的定义：\coordinate [label=right:$\theta$] (Theta) at ({#1/2}:\@arclen+.1);。Theta 现在设置为给定角度的一半（#1我希望您还记得，即！）。
现在我可以绘制三角形了。由于角度本身已经定义，我可以使用该角度在连接点“A”和“B”的线上倾斜标签。
再次强调：由于角度是精确已知的，我不必冒险将弧线画得更长，并剪掉所有突出的部分。因此，clip删除了上述 MWE 中的 -command。

我还定义了一些内部变量\@triaglen、\@sqlen和\@arcradii，以便能够一致地更改三角形的大小。要使用@- 符号，我必须使用\makeatletter和\makeatother。如果您在样式文件中隐藏\newcommands 和\defs ，则不必提供\makeatletter和\makeatother。的用法@是使这些命令和变量成为“内部”的。要更改三角形大小，我添加了一个用户空间命令\trianglelength{}，它接受一个参数，即斜边的新长度。

我在第一个三角形中演示了的用法\trianglelength。请注意，新大小仅限于该三角形subfigure，不会影响第二个和第三个三角形。

这是完整的高级 MWE。（正如评论中指出的那样，我更改了标题的布局，使其对齐而不是居中。）

\documentclass{report}
\usepackage[a4paper,width=150mm,top=25mm,left=15mm,bottom=25mm,right=15mm,bindingoffset=10mm]{geometry}
\usepackage{subcaption}
\usepackage{tikz}
\usetikzlibrary{shapes.geometric, decorations.pathreplacing, matrix,
  angles, quotes, arrows, arrows.meta, datavisualization} 
\usepackage{pgfplots}

%% better to be defined in the preamble?
\captionsetup{font=footnotesize}%

%% Te speed up the programming: define this command, to draw a
%% triangle.  The arguments denote:
%%      #1: angle of the triangle (0°--90°)
%%      #2: label of the AC-line (hypothenuse)
%%      #3: label of the CB-line (opposite line, Gegenkathethe)
%%      #4: label of the AB-line (adjacent line, Ankathethe)
%% Now the Point A will be in the origin.  To get this working, I will
%% use polar coordinates.  To be more flexible, I define the internal
%% factor \@triaglen, which is the length of the hypothenuse.  Derived
%% from that are \@sqlen, the size of the square corner rectangle and
%% \@arcradii, the radius of the angle arc.
\makeatletter%
\def\@triaglen{3.0}%
\def\@sqlen{\@triaglen/12}%
\def\@arcradii{\@triaglen/5}%
\newcommand{\triang}[4]{%
  \begin{tikzpicture}[scale=1.0%
    % ,cap=round
    % ,>=latex
    ]%
    %% first point "A" is the origin
    \coordinate [label=left:$A$] (A) at (0,0);%
    %% second is the polar coordinate of the angle given in #1, and a
    %% freely defined length in \@triaglen
    \coordinate [label=above:$B$] (B) at (#1:\@triaglen);%
    %% The last point is the intersection of a vertical line through
    %% the second point and the x-axis.  This is denoted in TikZ with
    %% "|-".  See the TikZ-manual/tutorial on page 38
    \coordinate [label=right:$C$] (C) at (#1:\@triaglen |- 0,0);%
    %% coordinates of the angle Theta.  Theta should be in the middle
    %% between x-axis and the hpothenuse, which is in polar
    %% coordinates the half of #1: #1/2
    \coordinate [label=right:$\theta$] (Theta) at ({#1/2}:\@arcradii+.1);%
    %% draw the trinangle
    \draw (A) -- node[above, rotate=#1] {#2} (B) -- node[right] {#3} (C) --%
    node[below] {#4} (A);%
    %% draw the rectangular corner
    \draw[thin] (C) rectangle +(-\@sqlen,\@sqlen);%
    %% Draw the angle arc
    \draw[thin] (A) -- (\@arcradii,0)  arc[start angle=0,
    end angle=#1, radius=\@arcradii] --  cycle;
  \end{tikzpicture}%
}
%% This could be a user space command, to change the length of the
%% hypothenuse
\newcommand{\triaglength}[1]{%
  \def\@triaglen{#1}}%
\makeatother


\begin{document}
\begin{figure}
  \centering
  \begin{subfigure}[b]{0.3\linewidth}
    \centering
    %% Change the size of the triag (local to this subfigure)
    \triaglength{4.0}
    \triang{30}{$c$}{$a$}{$\sqrt{c^{2}-a^{2}}$}
    \caption{$a=c \sin\theta$}
  \end{subfigure}%
  \begin{subfigure}[b]{0.3\linewidth}
    \centering
    \triang{40}{$\sqrt{a^2 + b^2}$}{$a$}{$b$}
    \caption{$Bu=c \cos \theta$}
  \end{subfigure}%
  \begin{subfigure}[b]{0.3\linewidth}
    \centering
    \triang{50}{$c$}{$\sqrt{c^2 - b^2}$}{$b$}
    \caption{$a=\sqrt{c^2 - b^2}$}
  \end{subfigure}
  %% Now the main caption.  Of course, captions may have more than one line.
  \caption{Triangle calculations by means of trigonometric functions.\\
  To utilize trigonometric functions, you'll have to apply them on a
  triangle, which has a right angle.  There are the functions Sinus,
  Cosinus and Tanges.  Sinus is defined as the fraction of the length
  of the opposite site to the length of the hypothenuse.}
  \label{fig:triangle}
\end{figure}
\end{document}

其结果如下：

Answer 1