
Dayv O. answered 04/23/22
Attentive Reliable Knowledgeable Math Tutor
need region in xy plane to evaluate any double integral f(x,y)dxdy.
reason, say dx part evaluated first and ∫f(x,y)dx=F(x,y)+C(y)
C can be a constant or any function of y.
example C=sin(y)+ey*cos(y)+y4+8
that makes evaluating the integral [F(x,y)+C(y)dy part impossible

Dayv O.
it isn't that the C(y) used as example is impossible to integrate, it is that all C(y) functions are valid C(y), It is impossible to choose C(y).04/23/22