\documentclass[border=1bp,varwidth]{standalone}
\usepackage{tikz,fp}
\usetikzlibrary{calc,angles,quotes}

\begin{document}


\begin{tikzpicture}
\coordinate (O) at (0,0);
\coordinate (P) at (5,-0.75);
\coordinate (X) at (0, -40pt);
\def\ptRadius{1.25pt}
\def\bigRadius{60pt}

\draw [fill] (O) circle (\ptRadius) node [left] {$O$};
\draw [fill] (P) circle (\ptRadius) node [above] {$P$};
\node [circle, draw] (Circ) at (P) [minimum size=\bigRadius] {};

\draw [->,>=stealth,thick] (O) -- (up:20pt);
\draw [->,>=stealth,thick] (O) -- (right:20pt);
\draw (O) -- (P);
\draw [densely dashed] (O) -- (X);

\draw []  (O) -- (tangent cs:node=Circ, point={(O)}, solution=1) coordinate (T) node [inner sep=0,below,anchor=north,yshift=-2pt] () {T};
\draw [<-,>=stealth,shorten >=0.9] (T) -- node [midway,right] (){$r$} (P);


%Draw the small square (not fully automatic yet: the 5 and 60!)
\def\vSide{5pt}
\draw [blue] (T) -- ($(T)!{2*5/60}!(P)$) -- ([turn]90:\vSide) -- ([turn]90:\vSide) -- cycle;


%Draw angles
\path (T) coordinate (A) -- (O) coordinate (B) -- (P) coordinate (C) pic [draw,<->,>=stealth,angle radius=1.25cm,"$\alpha$", angle eccentricity=1.15] {angle};

\path (X) coordinate (A) -- (O) coordinate (B) -- (T) coordinate (C) pic [draw,<->,>=stealth,angle radius=1.25cm,"$\theta$", angle eccentricity=1.15] {angle};

\path (X) coordinate (A) -- (O) coordinate (B) -- (P) coordinate (C) pic [draw,<->,>=stealth,angle radius=0.75cm,"$\beta$", angle eccentricity=1.25] {angle};


\end{tikzpicture}



\end{document}