The double integral problem of higher mathematics, where wavy lines are drawn, says that the problem has rotational symmetry. What conditions does it have?
Region D has rotational symmetry (that is, X and Y are interchangeable in the boundary curve equation of D, and the topic is X 2+Y 2 = 4. Geometrically, that is, when the two coordinate axes are interchanged and the figure remains unchanged), then ∫∫ f (x, y) dxdy = ∫∫ f (y, x) dxdy.