"
"
"
a, b " R2 I(a, b) a, b
I(A, B) = {I(a, b) : a " A, b " B}
A, B A B A ‚" (0, ") × {0}
x B ‚" {0} × (0, 2008) y I(A, B)
A B
X R2
" "
1 1
X = ({0} × [-1, 1]) *" ( { } × [-1, 0]) *" ( [0, an] × { }) ,
n n
n=1 n=1
an > 0
1
an = 1 - X
n+1
an X
 X
A = {(x, y, z) " R3 : 1 d" x2 + y2 + z2 d" 2}, X = R3
"
1
B = {(x, y) " R2 : y = x2}, X = R2
n
n=1
C = R2 \ {(x, y) " R2 : y = ctg x, x = kĄ, k = 0, ą1, ą2, . . . },

X = R2
D = {(x, y) " R2 : x2 + y2 = 1}, X = R2
X
X
X
X