size(0,150); pair z0=(0,0); real r=1; real h=1; real l=sqrt(r^2+h^2); real a=(1-r/l)*360; real a1=a/2; real a2=360-a/2; path g=arc(z0,r,a1,a2); fill((0,0)--g--cycle,lightgreen); draw(g); pair z1=point(g,0); pair z2=point(g,length(g)); real r2=1.1*r; path c=arc(0,r2,a1,a2); draw("$2\pi r$",c,red,Arrows,Bars,PenMargins); pen edge=blue+0.5mm; draw("$\ell$",z0--z1,0.5*SE,edge); draw(z0--z2,edge); draw(arc(z0,r,a2-360,a1),grey+dashed); dot(0);