\begin{tikzpicture}
\draw[help lines](0,0)grid(3,2);
\coordinate(a)at(0,1);
\coordinate(b)at(3,2);
\coordinate(c)at(2.5,0);
\coordinate(e)at($(a)!(c)!(b)$);
\draw[blue](c)--($(a)!(c)!(b)$);
\node[left](a)at(0,1){$A$};
\node[right](b)at(3,2){$B$};
\node[below](c)at(2.5,0){$C$};
\node[above](d)at($(a)!(c)!(b)$){$D$};
\end{tikzpicture}
提问于：
浏览数：
3408
2 回答
16
方法一：加载`angles`库
```tex
%\usetikzlibrary{angles}
\begin{tikzpicture}
\draw[help lines](0,0)grid(3,2);
\coordinate(a)at(0,1);
\coordinate(b)at(3,2);
\coordinate(c)at(2.5,0);
\coordinate(e)at($(a)!(c)!(b)$);
\draw[blue](c)--($(a)!(c)!(b)$);
\node[left]at(0,1){$A$};
\node[right]at(3,2){$B$};
\node[below]at(2.5,0){$C$};
\node[above]at($(a)!(c)!(b)$){$D$};
\draw pic[draw,scale=0.2]{right angle =b--e--c};%%绘制直角
\end{tikzpicture}
```
方法二
用`tkz-euclide`包的`angles`库
```tex
%\usepackage{tkz-euclide}
%\usetkzobj{angles}
\begin{tikzpicture}
\draw[help lines](0,0)grid(3,2);
\coordinate(a)at(0,1);
\coordinate(b)at(3,2);
\coordinate(c)at(2.5,0);
\coordinate(e)at($(a)!(c)!(b)$);
\draw[blue](c)--($(a)!(c)!(b)$);
\node[left]at(0,1){$A$};
\node[right]at(3,2){$B$};
\node[below]at(2.5,0){$C$};
\node[above]at($(a)!(c)!(b)$){$D$};
\tkzMarkRightAngle[scale=0.4](b,e,c)%%绘制直角
\end{tikzpicture}
```
-
第一种方法显示错误：! Package pgfkeys Error: I do not know the key '/tikz/pics/right angle', to whi ch you pas – yqc_1013 2019-11-05 16:10 回复
2
一个偷懒不嫌麻烦的办法，用 turn 选项：
```tex
\begin{tikzpicture}
\draw[help lines](0,0)grid(3,2);
\coordinate(a)at(0,1);
\coordinate(b)at(3,2);
\coordinate(c)at(2.5,0);
\coordinate(d)at($(a)!(c)!(b)$);
\path(c)--(d) -- ([turn]90:2mm) coordinate (t1) -- ([turn]90:2mm) coordinate (t2) -- ([turn]90:2mm) coordinate (t3);
\draw[blue](c)--(d);
\draw[red](t1)--(t2)--(t3);
\node[left](A)at(0,1){$A$};
\node[right](B)at(3,2){$B$};
\node[below](C)at(2.5,0){$C$};
\node[above](D)at(d){$D$};
\end{tikzpicture}
```
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