i.1.59 Double integrals
condition: Calculate the integral \( \iint_{\Delta}\left(x^{2}+y^{2}\right) d x d y \), if the area \( \Delta \) is limited by the lines \( y=x, x=0, y=1, y=2 \)
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.