documentclass[10pt]{amsart}
usepackage{amsmath}
usepackage{amsfonts}
usepackage{amssymb}
usepackage{amsthm}
usepackage{mathtools,array}

usepackage{tikz}
usetikzlibrary{calc,angles,positioning,intersections,quotes,decorations.markings}
usepackage{tkz-euclide}
usetkzobj{all}

usepackage{pgfplots}
pgfplotsset{compat=1.11}


begin{document}


begin{tikzpicture}begin{axis}
[width=6in,axis equal image,
    axis lines=middle,
    xmin=-10,xmax=10,samples=201,
    xlabel=$x$,ylabel=$y$,
    ymin=-4,ymax=6,
    restrict y to domain=-4:6,
    enlargelimits={abs=0.5cm},
    axis line style={latex-latex},
    ticklabel style={font=tiny,fill=white},
    xtick={empty},ytick={empty},
    xlabel style={at={(ticklabel* cs:1)},anchor=north west},
    ylabel style={at={(ticklabel* cs:1)},anchor=south west}
]
path (80:3) coordinate (a) (20:3.5) coordinate (b) (0:0) node[dot,label=below left:$P$]{} coordinate(P)(-100:1)coordinate (e) (-160:1) coordinate (f)(80:2) node [dot,label=above left:$A$]{} coordinate (A) (20:2.5) node [dot,label=below:$B$]{} coordinate (B) ($(P)!(A)!(B)$) coordinate [label=below:$Q$](Q);
draw[<->]  (a) node [above left ]{$l$} -- (e);
draw[<->]  (b) node [below right]{$k$} -- (f);

draw[purple!70!black,dashed] (A) -- (Q);
tkzMarkRightAngle(A,Q,P);

draw[|<->|] ($(P)!3mm!90:(A)$)--node[fill=white,sloped] {$r$} ($(A)!3mm!-90:(P)$);
draw[|<->|] ($(P)!-3mm!90:(Q)$)--node[fill=white,sloped] {$x$} ($(Q)!-3mm!-90:(P)$);
draw[|<->|] ($(Q)!-3mm!90:(A)$)--node[fill=white,sloped] {$y$} ($(A)!-3mm!-90:(Q)$);
path pic[draw, angle radius=5mm,"$theta$",angle eccentricity=1.25] {angle = B--P--A};
endend{axis}
end{tikzpicture}

end{document}