# How to draw arc inside a triangle with tikz?

I wonder how to draw something like this picture using tikz or tkz-euclide. I really don't have any clue what to do first.

• Thanks for editing my question. This is my first question. – masrosid Jun 13 '16 at 15:44

Labels are on you

\documentclass[tikz]{standalone}
\usetikzlibrary{calc}
\begin{document}
\begin{tikzpicture}
\filldraw (0,2) -- (2,0) -| cycle (0,0)
arc (270:315:2) coordinate(a)--($(a)!2!(45:{sqrt(2)})$) arc (135:180:2);
\end{tikzpicture}
\end{document}


• Thanks. But I need to learn it first, because there are some syntax I don't understand. – masrosid Jun 14 '16 at 8:25
• What about \filldraw(0,0)arc(270:315:2)--(0,2)--(0,0)arc(180:135:2)--(2,0)--(0,0); ? – Kpym Aug 31 '16 at 17:21
• Or \filldraw(,)arc(270:315:2)--(1,3)--(,)arc(180:135:2)--(3,1)--(,);, but I don't know why (,) is (1,1) and not (0,0) ... – Kpym Aug 31 '16 at 17:31

A solution without magic numbers (except for zero) and angle calculations.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{calc}

\begin{document}
\begin{tikzpicture}
% The corners of the triangle
% \Ay and \Cx are the length of the catheti of the right-angled triangle
% and the radius for the circles in A and C.
\def\Ay{2cm}
\def\Cx{2cm}
\path
(0, \Ay) coordinate (A)
(0, 0) coordinate (B)
(\Cx, 0) coordinate (C)
;

% The areas are filled by filling the two circles in A and B.
% Because of the "even odd rule", the intersection is not filled.
% The fill areas are limited to the triangle by clipping.
% The local overlay removes the larger circles from the bounding
% box calculations for the whole tikzpicture.
\begin{scope}[overlay]
\clip (A) -- (B) -- (C) -- cycle;
\fill[even odd rule]
;
\end{scope}

% The triangle is drawn.
\draw (A) -- (B) -- (C) -- cycle;

% The annotations with the point names.
\path
(A) node[above left] {$A$}
(B) node[below left] {$B$}
(C) node[below right] {$C$}
% The coordinates for D and E are calculated
% via the syntax of distance modifiers.
($(C)!\Cx!0:(A)$) coordinate (D) node[above right] {$D$}
($(A)!\Ay!0:(C)$) coordinate (E) node[above right] {$E$}
;

\end{tikzpicture}
\end{document}


Too verbose compared with percusse's solution but, I hope, not so cryptic.

\documentclass[tikz,border=2mm]{standalone}
\begin{document}
\begin{tikzpicture}
\draw (0,0) coordinate[label=above left:$A$] (A) --++(-90:2cm) coordinate[label=below left:$B$] (B) --++(0:2cm) coordinate[label=below right:$C$] (C) --cycle;

\fill (A)--(B) arc (180:135:2cm) coordinate[label=above right:$D$] (D)--cycle;

\fill (C)--(B) arc (-90:-45:2cm) coordinate[label=above right:$E$] (E)--cycle;
\end{tikzpicture}
\end{document}


• Hey !! who is cryptic here it is a compact river of of ideas :P – percusse Jun 15 '16 at 22:37