# Draw the unit circle using TikZ :

Well I'm preparing an article about trigonometry, unfortunately I'm not that much good with TikZ So I'm not able to draw it perfectly, So please some help so I can draw my circle ! and thanks in advance !

Here's the figure that I'd love to have it in my article !

\documentclass{article}

\usepackage{pgfplots}
\usetikzlibrary{intersections,angles,quotes}
\usepgfplotslibrary{fillbetween}
%\pgfplotsset{compat=1.17}

\begin{document}

\begin{tikzpicture}[scale=3]

%grid lines
\draw[
step=.5cm,
gray,
very thin
]
(-1.4,-1.4) grid (1.4,1.4);
\filldraw[
fill=blue!20,
draw=red!50
]
(0,0) -- (3mm,0mm)
arc [
start angle=0,
end angle=30,
-- cycle;
%axes
\draw[->] (-1.5,0) -- (1.5,0) coordinate (x axis);
\draw[->] (0,-1.5) -- (0,1.5) coordinate (y axis);

%axes label
\node [right]at (1.5,0)(x){$x$};
\node [above]at (0,1.5){$y$};

%circle
\draw (0,0) circle [
];

%triangle height
\draw[
very thick,
orange
]
(30:1cm) -- node[
left=1pt,
fill=white
]
{$\sin \alpha$} (30:1cm |- x axis);

%triangle base
\draw[
very thick,
blue
]
(30:1cm |- x axis) -- node[
below=2pt,
fill=white
]
{$\cos \alpha$} (0,0);

%intersection
\path [name path=upward line] (1,0) -- (1,1);
\path [name path=sloped line] (0,0) -- (30:1.5cm);
\draw [name intersections={of=upward line and sloped line, by=t}]
[very thick,red]
(1,0) -- node [right=1pt,fill=white]
{$\displaystyle \tan \alpha$} (t);
\draw (0,0) -- (t);

%x-ticks
\foreach \x/\xtext in {-1,
-0.5/-\frac{1}{2},
1}
\draw (\x cm,1pt) -- (\x cm,-1pt) node[
anchor=north,
fill=white
]
{$\xtext$};
%y-ticks
\foreach \y/\ytext in {-1,
-0.5/-\frac{1}{2},
0.5/\frac{1}{2},
1}
\draw (1pt,\y cm) -- (-1pt,\y cm) node[
anchor=east,
fill=white
]
{$\ytext$};
%arc angle
\draw (x) coordinate (A)--
(0,0) coordinate (B)--
(t) coordinate (C)
pic [
draw,
red,
"$\alpha$",
]
{angle};
\end{tikzpicture}

\end{document}


Using the example in the pgf manual cited by @jsbibra you only have to make slight modifications and then get:

\documentclass[tikz]{standalone}

\usetikzlibrary{intersections}

\begin{document}
\begin{tikzpicture}[scale=3]
\draw[step=.5cm,gray,very thin] (-1.4,-1.4) grid (1.4,1.4);
\filldraw[fill=blue!20,draw=red] (0,0) -- (3mm,0mm)
arc [start angle=0, end angle=30, radius=3mm] -- cycle;
\node[red] at (15:2mm) {$\alpha$};
\draw[->] (-1.5,0) -- (1.5,0) coordinate (x axis)node[right]{$x$};
\draw[->] (0,-1.5) -- (0,1.5) coordinate (y axis)node[above]{$y$};
\draw[very thick,orange]
(30:1cm) -- node[left=1pt,fill=white] {$\sin \alpha$} (30:1cm |- x axis);
\draw[very thick,blue]
(30:1cm |- x axis) -- node[below=2pt,fill=white] {$\cos \alpha$} (0,0);
\path [name path=upward line] (1,0) -- (1,1);
\path [name path=sloped line] (0,0) -- (30:1.5cm);
\draw [name intersections={of=upward line and sloped line, by=t}]
[very thick,red] (1,0) -- node [right=1pt,fill=white]
{$\displaystyle \tan \alpha$} (t);
\draw (0,0) -- (t);
\foreach \x/\xtext in {-1, -0.5/-\frac{1}{2}, 1}
\draw (\x cm,1pt) -- (\x cm,-1pt) node[anchor=north,fill=white] {$\xtext$};
\foreach \y/\ytext in {-1, -0.5/-\frac{1}{2}, 0.5/\frac{1}{2}, 1}
\draw (1pt,\y cm) -- (-1pt,\y cm) node[anchor=east,fill=white] {$\ytext$};
\end{tikzpicture}
\end{document}


Which produces: