# How to draw double integral functions

## Main Question or Discussion Point

Hi every one!

I would like to draw a double integral function in related to R and h parameters by below M-File but It does goes wrong!!!
Is there any one to correct it for me???
thank you

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))));

ezsurf(f,[0.001,5]);

Related MATLAB, Maple, Mathematica, LaTeX News on Phys.org
kai_sikorski
Gold Member
There's two problems that I can see right away (and perhaps more that I don't see). For one I'm guessing you're trying to make f a function of R and h? But you just leave them as symbolic objects. The second problem is that where you define the integrand, you need an extra "."

Code:
integrand = @(r,a)(h.*sin(a)./((r.^2).*(r.^2+h.^2-2.*r.*h.*cos(a))));

If I understand what you're trying to do correctly then this should do it:
Code:
f = @(h,R) quad2d(@(r,a)(h.*sin(a)./((r.^2).*(r.^2+h.^2-2.*r.*h.*cos(a)))),h,sqrt(R.^2+(R+h).^2),0,atan(R./(R+h)));
ezsurf(f,[0.001,5]);
When I ran it, there were a bunch of warnings but I think that may be due to a singularity in the integral you're evaluating.

Thank you very much.

your correctness lets the functions be drawn!!!!!