我有以下 MWE，基于在此站点上找到的答案来绘制切线，然后将切线延伸至轴：
\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\usetikzlibrary{calc,intersections,through,backgrounds,matrix,patterns}
\usepackage[normalem]{ulem}
\usetikzlibrary{decorations.pathreplacing}
\tikzset{mark tangent intersections with axes/.code={
\path let \p1=(tangent point-#1),
\p2=($(tangent unit vector-#1)-(tangent point-#1)$)
in
({\x1-\y1*\x2/\y2},0) coordinate (x-intersection-#1)
(0,{\y1-\x1*\y2/\x2}) coordinate (y-intersection-#1);},
mark tangent intersections with axes/.default=1
}
\begin{document}
\begin{tikzpicture}[scale = 1.2,
tangent/.style={
decoration={
markings,% switch on markings
mark=
at position #1
with
{
\coordinate (tangent point-\pgfkeysvalueof{/pgf/decoration/mark info/sequence number}) at (0pt,0pt);
\coordinate (tangent unit vector-\pgfkeysvalueof{/pgf/decoration/mark info/sequence number}) at (1,0pt);
\coordinate (tangent orthogonal unit vector-\pgfkeysvalueof{/pgf/decoration/mark info/sequence number}) at (0pt,1);
}
},
postaction=decorate
},
use tangent/.style={
shift=(tangent point-#1),
x=(tangent unit vector-#1),
y=(tangent orthogonal unit vector-#1)
},
use tangent/.default=1
]
\footnotesize
\draw[<->] (0,5) node[above]{$y$}--(0,0)--(5,0) node[right]{$x$};
\draw[name path = I1, tangent=0.5] (0.2,4) to [out=-85,in=180] (4.5,0.5) node[right] {IC$_3$};
\draw[mark tangent intersections with axes, red]
(x-intersection-1) -- (y-intersection-1);
\end{tikzpicture}
\end{document}
我希望在序言中定义切线的代码部分，这样我写代码时会更简洁、更简短。具体来说，这部分：
tangent/.style={
decoration={
markings,% switch on markings
mark=
at position #1
with
{
\coordinate (tangent point-
\pgfkeysvalueof{/pgf/decoration/mark info/sequence number}) at (0pt,0pt);
\coordinate (tangent unit vector-
\pgfkeysvalueof{/pgf/decoration/mark info/sequence number}) at (1,0pt);
\coordinate (tangent orthogonal unit vector-
\pgfkeysvalueof{/pgf/decoration/mark info/sequence number}) at (0pt,1);
}
},
postaction=decorate
},
use tangent/.style={
shift=(tangent point-#1),
x=(tangent unit vector-#1),
y=(tangent orthogonal unit vector-#1)
},
use tangent/.default=1
我怎样才能做到这一点？
答案1
正如@dalief 在评论中所说，您只需将这些行移到\tikzset{...}序言中的声明中：
\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\usetikzlibrary{calc,intersections,through,backgrounds,matrix,patterns}
\usepackage[normalem]{ulem}
\usetikzlibrary{decorations.pathreplacing}
\tikzset{mark tangent intersections with axes/.code={
\path let \p1=(tangent point-#1),
\p2=($(tangent unit vector-#1)-(tangent point-#1)$)
in ({\x1-\y1*\x2/\y2},0) coordinate (x-intersection-#1)
(0,{\y1-\x1*\y2/\x2}) coordinate (y-intersection-#1);},
mark tangent intersections with axes/.default=1,
tangent/.style={
decoration={
markings,% switch on markings
mark= at position #1 with
{
\coordinate (tangent point-\pgfkeysvalueof{/pgf/decoration/mark info/sequence number}) at (0pt,0pt);
\coordinate (tangent unit vector-\pgfkeysvalueof{/pgf/decoration/mark info/sequence number}) at (1,0pt);
\coordinate (tangent orthogonal unit vector-\pgfkeysvalueof{/pgf/decoration/mark info/sequence number})
at (0pt,1);
}
},
postaction=decorate
},
use tangent/.style={
shift=(tangent point-#1),
x=(tangent unit vector-#1),
y=(tangent orthogonal unit vector-#1)
},
use tangent/.default=1,
}
\begin{document}
\begin{tikzpicture}[scale = 1.2, every node/.append style={font=\footnotesize}]
\draw[<->] (0,5) node[above]{$y$}--(0,0)--(5,0) node[right]{$x$};
\draw[name path = I1, tangent=0.5] (0.2,4) to [out=-85,in=180] (4.5,0.5) node[right] {IC$_3$};
\draw[mark tangent intersections with axes, red] (x-intersection-1) -- (y-intersection-1);
\end{tikzpicture}
\end{document}
为了更好的衡量，我还添加了every node/.append style={font=\footnotesize}环境选项tikzpicture以应用于\footnotesize所有节点文本。当然，这也可以添加到语句中——如果您想这样做，请注意，您需要用逗号\tikzset{...}分隔里面的所有不同样式等。\tikzset{...}