C=1; K=1; P=1;
R1=10;
r1=9;
L=3.5;
e=3.3; x=-10:0.01:10; y=-10:0.01:10;
r2 = sqrt(x.^2+y.^2);
s=sqrt(e.^2+L.^2);
e1=linspace(0,e,length(r2));
s1=sqrt(L^2+e1.^2);
if r1-s<r2<R1
R=s.*C.*P.*(acos((r2.^2+s1.^2-r1.^2)./(2.*sqrt(x.^2+y.^2).*s1))+acos((s.^2+r2.^2-r1.^2)/(2.*r2.*s))...
-acos((s.^2+s1.^2-(e1+e).^2)/(2.*s.*s1)));
else 0<r2<r1-s
R=2.*pi.*s.*K.*P;
% else
% R=0;
end
surf(x,y,R);
xlabel('x'),ylabel('y'),zlabel('R(r2)');
title('3-D surf');