verbatimtex
  \documentclass{jsarticle}[16pt]
  \usepackage{txfonts}
  \begin{document}
 etex;
 
 
 u=1cm;
 pair i, j, k, l, O;
 b=1/3;
 g=1/sqrt(1-(b**2) );
 O=(0,0);
 
 i=(1,0)*u;
 j=(0,1)*u;
 
 k=( g, g*b )*u;
 l=( g*b, g )*u;
 
 beginfig(0);
 
 fill -3l/g -- 3l/g -- 3l/g + 1.5i/g -- -3l/g + 1.5i/g -- cycle withcolor 0.8[blue, white];
 
 drawarrow -3i -- 3i;
 label.llft(btex $x$ etex, 3i);
 drawarrow -3j -- 3j;
 label.llft(btex $w$ etex, 3j);
 label.ulft(btex $O$ etex, O);
 
 drawarrow -3k/g -- 3k/g;
 label.llft(btex $x'$ etex, 3k/g);
 drawarrow -3l/g -- 3l/g;
 label.llft(btex $w'$ etex, 3l/g);
 
 draw 1.5i
 for t=0 step 0.05 until 3: .. sqrt( (1.5**2)+(t**2) )*i+t*j endfor
 dashed evenly scaled 0.75pt;
 draw 1.5i
 for t=0 step -0.05 until -3: .. sqrt( (1.5**2)+(t**2) )*i+t*j endfor
 dashed evenly scaled 0.75pt;
 
 draw O -- 1.5k withcolor blue;
 draw O -- 1.5i/g withcolor blue;
 label.ulft(btex $l$ etex, 1.5k);
 label.urt(btex $l$ etex, 1.5i);
 label.llft(btex $\frac{l}{\gamma}$ etex, 1.5i/g);
 
 endfig;
 
 end.