input TEX;

u:=0.7cm;
t:=1.5pt;
r:=2pt;

beginfig(1);
u:=0.5cm;
z0=(0,0);
z2=z0+7u*dir0;
z1=z2+5u*dir90;
z3=4u*dir35.537677792;
fill (0,0)--4u*dir0--z3--cycle withcolor 0.5[black,white];
draw  for i=0 step 10 until 350:  4u*dir i..  endfor  cycle;
draw 4u*dir0--z3;
draw z0--z2--z1--cycle;
draw z2+0.5u*dir180--z2+sqrt(2)*0.5u*dir135--z2+0.5u*dir90;
drawdblarrow z0+0.3u*dir-90--z2+0.3u*dir-90;
label.bot(btex7 in.etex, 0.7[z0+0.3u*dir-90,z2+0.3u*dir-90]);
drawdblarrow ((0,0)+0.3u*dir(32+90))--(z3+0.3u*dir(35.537677792+90));
label.ulft(btex4 in.etex, 0.5[(z0+0.3u*dir(32+90)),(z3+0.3u*dir(32+90))]);
label.rt(btex5 in.etex, 0.5[z1,z2]);
endfig;

bye