원과 접선(3)

\begin{tikzpicture}
[+preamble]
\usepackage{pgfplots}
\pgfplotsset{compat=newest}
[/preamble]

\begin{axis}[
ticks=none,
xmin=-2,
xmax=2,
ymin=-2,
ymax=2,
axis equal,
axis lines=middle,
xlabel=$x$,
ylabel=$y$,
disabledatascaling]
\draw[solid] (0,0) circle (1);
\path [draw=none,fill=white, fill opacity = 0] (0,0) circle (1);
\draw (0,0)--({cos(45)},{sin(45)}) node[left, pos=0.5]{$\scriptstyle r$};
\addplot[solid,domain=0.2:cos(45),<--] {-1*x+cos(45)+sin(45)} node[right, pos=0.2]{$\scriptstyle wt$};

\end{axis}
\end{tikzpicture}