2

1
lim x + l2(dxdy),
n"
ny
A
A (1, 1), (2, 1), (1, 2).
n

x + y
lim 1 + x l2(dxdy),
n"
5
A
A = {(x, y); 1 < x < 2; -1 < y - x < 1}.
n

x2 + y2
lim l2(dxdy),
n"
2
An
1 1
An = {(x, y); |x| d" 1 - , |y| d" 1 - }.
n n

x + y
(1 + )ne-x-y-z l3(dxdydz).
n
A
A = {(x, y, z); 0 < x + y < 1, z > 0}
A = {(x, y, z); 0 < x + y < 1, z > 0, x > 0, y > 0}.

lim (1 - sinn(x + y))xy2 l2(dxdy),
n"
A
A = {(x, y); 0 d" x d" 1, x e" y2}.

n
fn(x, y) = x2 + y2 I(0,")(xy) + (1 - x2 - y2)nI(-",0](xy).

limn" U fn(x, y)l2(dxdy) U = {(x, y); x2 + y2 d" 1}.


xyz
x y2
lim n sin exp - - - z l3(dxdydz),
n"
n2 2 4
S
S = {(x, y, z); x e" 0, y e" 0, z e" 0}.