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I want to use the example in http://www.texample.net/tikz/examples/morleys-triangle/. I changed the tkz-2d into tkz-euclide (as tkz-2d is superseeded by this package), but tkz-euclide doesn't know \tkzMathLength. How can I modify the code to get a working example?

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If \tkzMathLength is doing what I understood, you can use veclen from calc library and customize it to make up your own length computing command. See pgf manual (v.3.10) p.537 for further details. –  percusse Sep 18 '11 at 11:27
    
thank you so much ! –  Pig Cry Sep 18 '11 at 12:30
    
you are welcome. We should thank @Altermundus for that :) –  percusse Sep 18 '11 at 17:18
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1 Answer 1

up vote 1 down vote accepted

In tkz-euclide the legth of a segment is determined via:

\tkzCalcLength[<unit>](<point1>,<point2>) \tkzGetLength{<variableName>}

As you can see, you can also specify the unit in which you want the result. And, of course, don't forget the \ before <variableName>, when using it later in the code. :)

Edit: To avoid errors at compilation, you will need to specify the unit every time you use \<varialbleName>, e.g.:

\tkzCalcLength(R,Q) \tkzGetLength{dRQ}
\tkzCalcLength[cm](M,Q) \tkzGetLength{dMQ}

\tkzDrawCircle[R](O,\dRQ cm)
\tkzDrawCircle[R](P,\dMQ pt)

Edit2: OK, here is the full working example, in case it doesn't work for somebody:

% Morley's triangle
% Author : Arnaud Lefebvre (IREM Rouen)
% Ported to tkz-euclide : Count Zero
% Intersections of trisector lines in any triangle
% are vertices of an equilateral triangle

\documentclass{article}

\usepackage{tkz-euclide}

\usetikzlibrary{calc,intersections}
\usetkzobj{all}

\pagestyle{empty}

\begin{document}

\begin{tikzpicture}

%----------------------------------------------------
% Coordinates of A, B and C, the triangle vertices 
%----------------------------------------------------
\coordinate[label=above:$A$] (A) at (5,4);
\coordinate[label=left:$B$] (B) at (0,0);
\coordinate[label=right:$C$] (C) at (7,0);

%----------------------------------------------------
% Lengths of segments [AB], [BC], and [CA] 
%----------------------------------------------------
\tkzCalcLength(B,C) \tkzGetLength{a}
\pgfmathsetmacro{\la}{.01*\a pt}
\tkzCalcLength(A,C) \tkzGetLength{b}
\pgfmathsetmacro{\lb}{.01*\b pt}
\tkzCalcLength(A,B) \tkzGetLength{c}
\pgfmathsetmacro{\lc}{.01*\c pt}

%----------------------------------------------------
% Computing 1/3 of each angle
%----------------------------------------------------
\pgfmathsetmacro{\A}{acos((\la*\la-\lb*\lb-\lc*\lc)/(-2*\lb*\lc))};
\pgfmathsetmacro{\tA}{\A/3};
\pgfmathsetmacro{\B}{acos((\lb pt*\lb pt-\la pt*\la pt-\lc pt*\lc pt)/(-2*\la pt*\lc pt))};
\pgfmathsetmacro{\tB}{\B/3};
\pgfmathsetmacro{\C}{acos((\lc pt*\lc pt-\lb pt*\lb pt-\la pt*\la pt)/(-2*\lb pt*\la pt))};
\pgfmathsetmacro{\tC}{\C/3};

%----------------------------------------------------
% Computing intersections of trisector lines
%----------------------------------------------------
\coordinate (A1) at ($(A)!100*max(\lb pt,\lc pt)!\tA:(B)$);
\coordinate (A2) at ($(A)!100*max(\lb pt,\lc pt)!2*\tA:(B)$);
\coordinate (B1) at ($(B)!100*max(\la pt,\lc pt)!\tB:(C)$);
\coordinate (B2) at ($(B)!100*max(\la pt,\lc pt)!2*\tB:(C)$);
\coordinate (C1) at ($(C)!100*max(\la pt,\lb pt)!\tC:(A)$);
\coordinate (C2) at ($(C)!100*max(\la pt,\lb pt)!2*\tC:(A)$);

%----------------------------------------------------
% Computing coordinates of vertices O, P and Q of 
% the Morley's triangle 
%----------------------------------------------------
\coordinate (O) at (intersection of C--C1 and A--A2);
\coordinate (P) at (intersection of A--A1 and B--B2);
\coordinate (Q) at (intersection of B--B1 and C--C2);

%----------------------------------------------------
% Drawing triangles and trisectors
%----------------------------------------------------
\tkzMarkAngle[size=1,fill=green!80](B,A,A1)
\tkzMarkAngle[size=.9,fill=green!80](A1,A,A2)
\tkzMarkAngle[size=.8,fill=green!80](A2,A,C)
\tkzMarkAngle[size=1,fill=blue!80](C,B,B1)
\tkzMarkAngle[size=.9,fill=blue!80](B1,B,B2)
\tkzMarkAngle[mkpos=.2,size=.8,fill=blue!80](B2,B,A)
\tkzMarkAngle[size=1,fill=red!80](A,C,C1)
\tkzMarkAngle[size=.9,fill=red!80](C1,C,C2)
\tkzMarkAngle[size=.8,fill=red!80](C2,C,B)

\draw (A)--(B)--(C)--cycle;
\draw[fill=orange, opacity=.4] 
   (O)--node[sloped]{\tiny{//}}
   (P)--node[sloped]{\tiny{//}}
   (Q)--node[sloped]{\tiny{//}}(O);
\draw (A)--(O) (A)--(P) (B)--(P) (B)--(Q) (C)--(Q) (C)--(O);

%----------------------------------------------------
% Caption
%----------------------------------------------------
\node[rounded corners, fill=purple!20,anchor=south east] at (3,3) 
   {\begin{minipage}{5cm}
 \textbf{Morley's triangle}\newline In any triangle, trisector 
 lines intersect in 3 points that are vertices of an 
 equilateral triangle.
   \end{minipage}};

\end{tikzpicture}

\end{document}

So, no more complaints will be accepted! All right, just kidding... ;)

share|improve this answer
    
thanks a lot. now I know how to get the length. But a new problem comes out, "Dimension too large", I change the length to cm, it doesn't work. sigh…… :) –  Pig Cry Sep 18 '11 at 12:29
    
Hmmm... seems there is some extra detail that you need to take care of... and I overlooked it. Check the edit of my answer! –  Count Zero Sep 18 '11 at 12:35
    
thanks, I get it ! ^_^ –  Pig Cry Sep 18 '11 at 13:32
    
\tkzMarkAngle[mkpos=.2,size=.8,fill=blue!80](B2,B,A), without mkpos=.2, the code still has "Dimension too large" problem, but we can continue running the code and get the pdf file. Another way is to use \tkzFillAngle instead, \tkzFillAngle[size=.8,fill=blue!80](B2,B,A). –  Pig Cry Sep 19 '11 at 4:33
    
@Pig Cry: That's right. It's documented in the tkz-euclide manual and is seen with small angles. The work-around I applied is also suggested by the author, @Altermundus. –  Count Zero Sep 19 '11 at 8:55
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