How can I draw using tikz

Question

I am very beginner in tikz ! I want to draw picture with tikz:

Answer 1

You can take advantage of calc and intersections library to draw this picture.

\documentclass[margin=5mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{calc,intersections}


\begin{document}
\begin{tikzpicture}[>=stealth]

\coordinate (O) at (0,0);

\draw (-120:2)coordinate (B) arc (-120:120:2)coordinate(C);

\draw[<->] (-120:2.3) arc (-120:120:2.3)node[midway,fill=white]{$\beta$};

\path[name path=line1](C)--($(C)!2!-90:(O)$);
\path[name path=line2](O)--+(-5,0);

\fill [name intersections={of=line1 and line2}]
(intersection-1) circle (1.5pt);

\foreach \i in {O,B,C}
{\fill (\i)circle(1.5pt);}

\draw (B)--(intersection-1)--(C);
\draw [dashed](C)--(O)--(intersection-1);

\draw($(C)!0.1!(O)$)coordinate(c1)--($(c1)!1!90:(C)$)coordinate(c2)--($(c2)!1!90:(c1)$);

\draw[<->] (intersection-1)+(1,0)arc(0:30:1)node[midway,right,font=\scriptsize]{$\alpha$};

\draw[<->] ($(intersection-1)!0.3cm!90:(C)$)--($(C)!0.3cm!-90:(intersection-1)$)node[midway,sloped,fill=white]{$d/r$};

\end{tikzpicture}
\end{document}

Output

Answer 2

I started using tikz a while ago and i found great joy in doing the tutorials of the outstanding official documentation:

Official tikz & pgf documentation

The tutorials (starting at page 29) cover about everything that you need to do.

If you prefer less text there's also a great introduction to tikz, called "A very minimal introduction to Tikz:

Minimal Introduction to Tikz