用箭头标记锐角

Question

您将如何标记如下角度，

梅威瑟：

documentclass[tikz]{standalone}
\usepackage{pgf}
\usepackage{pgfplots}
\usetikzlibrary{calc,arrows,positioning}
\usepackage{tkz-euclide}
\usetkzobj{all}
\pgfplotsset{compat=1.11}


\begin{document}
    \begin{tikzpicture}[scale=0.6]
        \coordinate [label={[label distance=-3pt]45:{$O$}}] (O) at (0,0);
        \coordinate [label=above:N] (N) at (0,1.5);
        \coordinate (N') at (0,-1.5);
        \coordinate (E') at (-1.5,0);
        \coordinate (E) at (1.5,0);
        \draw[dashed] (E) -- (E');
        \draw[dashed] (O) -- (N);
        \coordinate [label={[label distance=0pt]-90:{$B$}}] (B) at (-120:5);
        \coordinate [label={[label distance=-3pt]-45:{$A$}}] (A) at ($(B)+(2.5,0)$);
        \draw (B) -- (A) -- (O);
        \draw (O) -- (B);
        \tkzLabelAngle[pos=2.5](B,O,A){$30^\circ$};
        \tkzMarkAngle[size=0.7](B,O,A);
        \end{tikzpicture}
\end{document}

这使：

Answer 1

您可以玩弄线条的出射角度和入射角度。

\begin{tikzpicture}[scale=0.6]
  \coordinate [label={[label distance=-3pt]45:{$O$}}] (O) at (0,0);
  \coordinate [label=above:N] (N) at (0,1.5);
  \coordinate (N') at (0,-1.5);
  \coordinate (E') at (-1.5,0);
  \coordinate (E) at (1.5,0);
  \draw[dashed] (E) -- (E');
  \draw[dashed] (O) -- (N);
  \coordinate [label={[label distance=0pt]-90:{$B$}}] (B) at (-120:5);
  \coordinate [label={[label distance=-3pt]-45:{$A$}}] (A) at ($(B)+(2.5,0)$);
  \draw (B) -- (A) -- (O);
  \draw (O) -- (B);
  % \tkzLabelAngle[pos=2.5](B,O,A){$30^\circ$};
  \tkzMarkAngle[size=0.7](B,O,A);
  \draw[stealth-] (-105:0.7) to[out=-90,in=-150,looseness=1.7] +(1,-0.3) node[anchor=west,inner sep=2pt]{$30^\circ$};
\end{tikzpicture}

作为替代，可以使用控制点来弯曲线条，例如

\draw[stealth-] (-105:0.7)  .. controls ++(0.05,-0.5) and ++(-0.6,-0.2) .. +(1,-0.3) node[anchor=west,inner sep=2pt]{$30^\circ$};