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I want to draw and label angle A (alpha) of my ABC triangle while still being able to change to coordinate of A B and C so that the angle and the mark adapts to it.

enter image description here

 \documentclass{article}
 \usepackage{pgfplots}
 \usetkzobj{all} %also needed
 \begin{document}
 \begin{tikzpicture}
 \coordinate (M) at (0,0) ;
 \coordinate (A) at (canvas polar cs:angle=90,radius=3cm) ;
 \coordinate (B) at (canvas polar cs:angle=-30,radius=3cm) ;
 \coordinate (C) at (canvas polar cs:angle=30,radius=3cm);
 \draw (M) circle (3cm);
 \draw (A) -- (B) -- (C) --cycle;
 \tkzDrawPoints(A,B,C,M);
 \tkzLabelPoints[above](A,C);
 \tkzLabelPoints(B,M);
 \tkzMarkAngle[fill= red,size=1.5cm, opacity=.4](B,A,C); %thanks to Claudio
 \tkzLabelAngle[pos = 0.8](B,A,C){$\alpha$};  
 \end{tikzpicture}
 \end{document}
Arne Timperman
  • 4,633
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    have a look at tkz-euclide. It's the best tool for such constructions – percusse Aug 24 '13 at 12:20
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    I think TikZ: Create right angle triangle with angle labels is a good starting point. – Claudio Fiandrino Aug 24 '13 at 12:21
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    In a question I asked some time ago (http://tex.stackexchange.com/a/124426/32245) there have been some nice solutions for calculated triangles and autorotated angle labels and so on... – LaRiFaRi Aug 24 '13 at 13:47
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    See also http://tex.stackexchange.com/questions/34640/best-way-to-create-this-image-square-and-angle/34673#34673 for some solutions. – Torbjørn T. Aug 24 '13 at 13:55
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    You can answer your own question below as a self-answer but, please, do not edit your question to include the answer in it. If you do, your question becomes incomprehensible to future visitors of this page. You want to leave them a trail of breadcrumbs as to what the problem originally was---that entails leaving your MWE intact, warts and all---before showing how it can be solved. – jub0bs Aug 24 '13 at 17:44

0 Answers0