# Drawing a TikZ arc specifying the center

The TiKz command for an arc:

\draw (0,0) arc (-30:30:2) ;


Draws an arc that starts at (0,0), and would be the part of the circle from -30 degrees to +30 degrees of radius 2.

It is very hard to place these arc sometimes. This is the symbol i want to draw:

(This represents an eye and needs more detail).

I want to draw the arc as _part of a circle with center at where the < meets, but I have to currently fudge the start location of the arc so it properly crosses the < (and it's not even exact).

If I could do a circle from -45 to +45 degrees CENTERED at the <, then that would be much easier.

Here is an answer, using the technique described here, with more detail,

\pgfmathsetmacro{\ex}{0}
\pgfmathsetmacro{\ey}{1}

\draw (\ex,\ey) -- ++(-15:1)
(\ex,\ey) -- ++(15:1);
\draw (\ex,\ey) ++(45:.8) arc (45:-45:.8);


The secret to this is in the last line,

\draw (\ex,\ey) ++(45:.8)


Jumps the draw cursor to "the 45 degree position on a circle of radius 0.8", without drawing anything (achieved by using only ++ and not any -- in the command)

Then, from there, we draw an arc

arc (45:-45:.8);


from 45 degrees to -45 degrees, of what would be a circle of radius .8.

Pretty roundabout way to do this, but still it works fine.

### Edit:

My finished eye:

\begin{tikzpicture}

%eye
\pgfmathsetmacro{\eyeSize}{1}
\pgfmathsetmacro{\ex}{0}
\pgfmathsetmacro{\ey}{1}
\pgfmathsetmacro{\eRot}{-10}
\pgfmathsetmacro{\eAp}{-55}
\draw[rotate around={\eRot:(\ex,\ey)}] (\ex,\ey) -- ++(-.5*\eAp:\eyeSize)
(\ex,\ey) -- ++(.5*\eAp:\eyeSize);
\draw (\ex,\ey) ++(\eRot+\eAp:.75*\eyeSize) arc (\eRot+\eAp:\eRot-\eAp:.75*\eyeSize);

% IRIS
\draw[fill=gray] (\ex,\ey) ++(\eRot+\eAp/3:.75*\eyeSize) % start point
arc (\eRot+180-\eAp:\eRot+180+\eAp:.28*\eyeSize);

%PUPIL, a filled arc
\draw[fill=black] (\ex,\ey) ++(\eRot+\eAp/3:.75*\eyeSize) % start point
arc (\eRot+\eAp/3:\eRot-\eAp/3:.75*\eyeSize);

\end{tikzpicture}


Now as TikZ 3.0 is here we can use pic.

\documentclass[tikz,border=5]{standalone}
\tikzset{
pics/carc/.style args={#1:#2:#3}{
code={
\draw[pic actions] (#1:#3) arc(#1:#2:#3);
}
}
}
\begin{document}
\begin{tikzpicture}
\pic{carc=-30:30:2cm};
\draw[thick] (4,0) circle (1 cm) pic[red, -latex]{carc=100:150:1.3cm};
\end{tikzpicture}
\end{document}


Note 1: This question was treated before here How to extend TikZ drawing commands

Note 2: I arrived here from this closed quastion Tikz: Curved parallel arrow around a circle, so I gave the answer here too.

EDIT: Here are some examples how we can use carc to create logos ;)

\documentclass[varwidth,border=50]{standalone}
\usepackage{tikz}
\tikzset{
pics/carc/.style args={#1:#2:#3}{
code={
\draw[pic actions] (#1:#3) arc(#1:#2:#3);
}
}
}
\begin{document}
\begin{tikzpicture}
\begin{scope}[xshift=-1.5cm]
\fill[orange, rounded corners=5mm] (-0.5,-0.5) rectangle (3.7,3.7);
\fill[white] (0.5,0.5) circle (0.5);
\draw[white, line width=7mm] (0,0) pic{carc=0:90:1.9} pic{carc=0:90:3};
\end{scope}

\begin{scope}[yshift=-4cm, yellow, line width=1.4cm]
\fill[black] circle (2.5);
\fill circle (.5);
\draw pic{carc=-60:0:1.4} pic{carc=60:120:1.4} pic{carc=180:240:1.4};
\end{scope}

% --- Wi-Fi
\begin{scope}[yshift=-10cm, purple, line width=7mm]
\fill circle (0.5);
\foreach \d in  {0,1,2}
\draw pic{carc=135:225:1.55+1.4*\d} pic{carc=-45:45:1.55+1.4*\d};
\pic[line width=3.9cm]{carc=-105:-75:3.1};
\end{scope}

\begin{scope}[yshift=-21cm, blue]
\fill (0,0) circle (0.5);
\foreach \d in  {0,1,2}
\draw[line width=7mm, line cap=round] (0,0) pic{carc=45:135:1.55+1.4*\d};
\end{scope}

% --- Goethe Institut
\begin{scope}[yshift=-25cm, xshift=-5cm, green, line width=1.25 mm]
\draw (2.5,2.5) circle (0.5);
\foreach \d in  {0,1,...,4}
\draw (1.5,1.5) pic{carc=90:360:0.5+0.25*\d};
\node[anchor=north west, scale=2, black, draw] at (3.2,1.6) {\textsf{GOETHE-INSTITUT}};
\end{scope}

% --- off
\begin{scope}[yshift=-29cm, line width=7mm, line cap=round]
\draw[black] (0,0) pic{carc=130:410:2};
\draw[red] (0,0) -- (0,2.2);
\end{scope}

\end{tikzpicture}
\end{document}