i.1.78 Double integrals
Condition: Calculate the double integral of the function \( f(x, y) \) over the specified rectangular area: \[ f(x, y)=\frac{1}{(x+y)^{2}}, \quad x \in[3,4], \quad y \in[1,2] \]
Double and iterated integrals over various areas of integration, conversion from Cartesian to polar coordinates, calculation of the Jacobian, changing the limits of integration, transformation of variables in the integral.