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Hi Guan,

That was a very good question. When dealing with multiple variables in an integration scenario, it is crucial to ensure that all variables are appropriately handled to achieve accurate results. In this case, the variable w appears in the integrand function, which might complicate the integration process if left unaddressed.To address the issue of the stuck variable w, one approach could involve separating the integration steps for x and y from the part of the code that involves w. By isolating the integrations for x and y, you can focus on resolving any dependencies on w separately.

Here is a modified version of the code snippet that separates the integration of x and y from the part involving w:

% Define the integrand function without the variable w

P1 = @(x, y) cos((m * pi * y) / a) * cos(2 * (x - y) / v);

% Perform integration for x and y separately

int_x = integral2(@(x, y) P1(x, y), Lb + l(s), Lb + l(s + 1), Lb + l(t), Lb + l(t + 1));

int_y = integral2(@(x, y) P1(x, y), Lb + l(s), Lb + l(s + 1), Lb + l(t), Lb + l(t + 1));

% Proceed with further computations using int_x and int_y

Please let me know if you have any further questions.