v
c
u
t
w
r
a
n
g
e
0
≤
w
≤
π
2
s
u
r
f
a
c
e
{
c
o
s
(
v
)
s
i
n
(
2
w
)
,
s
i
n
(
v
)
s
i
n
(
w
)
,
c
o
s
(
w
)
}
v
e
c
t
o
r
f
i
e
l
d
F
(
x
,
y
,
z
)
=
(
x
,
0
,
0
)
∫
∫
∫
d
i
v
(
F
)
d
V
=
1
.
5
7
0
8
f
l
u
x
=
∫
∫
F
·
n
d
S
=
1
.
5
7
0
8