draw a double integral function

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MatLab

Hi every one!
I have an double integral function and would like to draw it in matlab by different values of R and h parameters
I used below M-File but it doesn't work! would you guide me to repair it?

syms R h;
a1 = 0;
a2 = atan(R./(R+h));

r1 = h;
r2 = sqrt(R.^2+(R+h).^2);

integrand = @(r,a)(h.*sin(a)/((r.^2).*(r.^2+h.^2-2.*r.*h.*cos(a))));
f = quad2d(integrand,r1,r2,a1,a2);
ezsurf(f,[0.001,5]);