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TikZ：在两条线的平行位置添加坐标

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TikZ：在两条线的平行位置添加坐标

我想添加一个坐标，v\cos(\gamma)如果一条线从点开始，平行于我的线将位于P7该坐标处。但我不确定如何将这两条线移动到与我的原始线平行的位置。

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{calc, intersections, arrows}
\begin{document}
\begin{tikzpicture}[line cap = round, line join = round, >=triangle 45,
  scale = 1.25]
  \coordinate (O) at (0, 0);
  \coordinate (P1) at ($(O) + (-30:1.5cm and .75cm)$);

  \draw[-latex] (P1) arc (-30:310:1.5cm and .75cm) coordinate (P2);
  \draw[-latex] (O) -- (0, 1.75) node[above, scale = .75] {\(\mathbf{h}\)};
  \draw ($(P1)!.5!(P2)$) circle (.18cm) coordinate (P3);
  \draw[blue] (O) -- ($(P3)!.18cm!(O)$) node[scale = .75, pos = .5,
    fill = white, inner sep = 0cm] {\(\mathbf{r}\)} coordinate (P4);
  \draw[dotted, blue, name path = line] (P4) -- ($(P4)!.36cm!(P3)$)
  coordinate (P5);
  \path[name path = aux] (P5) circle [radius = 1bp];
  \draw[name intersections = {of = line and aux}, -latex, blue] (P5) --
  ($(intersection-1)!.5cm!(P5)$) node[scale = .75, shift = {(.25cm, -.2cm)}]
  {\(v\cos(\gamma)\)};
  \draw[dotted, name path = line2, blue] ($(P4)!.5!(P5)$) -- (P1)
  coordinate (P6);
  \path[name path = aux2] (P6) circle [radius = 1bp];
  \draw[name intersections = {of = line2 and aux2}, -latex, blue] (P6) --
  ($(intersection-1)!.75cm!(P6)$) node[scale = .75, shift = {(.25cm, .2cm)}]
  {\(v\sin(\gamma)\)} coordinate (P7);
\end{tikzpicture}
\end{document}

在此处输入图片描述

答案1

如果箭头的终点cos(\gamma)称为P8，则可以使用该calc库来计算该箭头的起点和终点的差向量（P5和P8），然后将其用作相对坐标（使用+运算符）：

\draw [red, -latex] (P7) -- +($(P8)-(P5)$);


\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{calc, arrows, intersections}
\begin{document}
\begin{tikzpicture}[line cap = round, line join = round, >=triangle 45,
  scale = 1.25]
  \coordinate (O) at (0, 0);
  \coordinate (P1) at ($(O) + (-30:1.5cm and .75cm)$);

  \draw[-latex] (P1) arc (-30:310:1.5cm and .75cm) coordinate (P2);
  \draw[-latex] (O) -- (0, 1.75) node[above, scale = .75] {\(\mathbf{h}\)};
  \draw ($(P1)!.5!(P2)$) circle (.18cm) coordinate (P3);
  \draw[blue] (O) -- ($(P3)!.18cm!(O)$) node[scale = .75, pos = .5,
    fill = white, inner sep = 0cm] {\(\mathbf{r}\)} coordinate (P4);
  \draw[dotted, blue, name path = line] (P4) -- ($(P4)!.36cm!(P3)$)
  coordinate (P5);
  \path[name path = aux] (P5) circle [radius = 1bp];
  \draw[name intersections = {of = line and aux}, -latex, blue] (P5) --
  ($(intersection-1)!.5cm!(P5)$) coordinate (P8) node[scale = .75, shift = {(.25cm, -.2cm)}]
  {\(v\cos(\gamma)\)};
  \draw[dotted, name path = line2, blue] ($(P4)!.5!(P5)$) -- (P1)
  coordinate (P6);
  \path[name path = aux2] (P6) circle [radius = 1bp];
  \draw[name intersections = {of = line2 and aux2}, -latex, blue] (P6) --
  ($(intersection-1)!.75cm!(P6)$) node[scale = .75, shift = {(.25cm, .2cm)}]
  {\(v\sin(\gamma)\)} coordinate (P7);
  \draw [red, -latex] (P7) -- +($(P8)-(P5)$);
\end{tikzpicture}
\end{document}

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