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Arnold's Trivium
1991 Arnold's Trivium
39
Problem 39
Problem 39
Source:
July 1, 2010
Gauss
calculus
integration
trigonometry
Problem Statement
Calculate the Gauss integral
∮
(
d
A
→
,
d
B
→
,
A
→
−
B
→
)
∣
A
→
−
B
→
∣
3
\oint\frac{(d\overrightarrow{A},d\overrightarrow{B},\overrightarrow{A}-\overrightarrow{B})}{|\overrightarrow{A}-\overrightarrow{B}|^3}
∮
∣
A
−
B
∣
3
(
d
A
,
d
B
,
A
−
B
)
where
A
→
\overrightarrow{A}
A
runs along the curve
x
=
cos
α
x=\cos\alpha
x
=
cos
α
,
y
=
sin
α
y=\sin\alpha
y
=
sin
α
,
z
=
0
z=0
z
=
0
, and
B
→
\overrightarrow{B}
B
along the curve
x
=
2
cos
2
β
x=2\cos^2\beta
x
=
2
cos
2
β
,
y
=
1
2
sin
β
y=\frac12\sin\beta
y
=
2
1
sin
β
,
z
=
sin
2
β
z=\sin2\beta
z
=
sin
2
β
.Note: that
∮
\oint
∮
was supposed to be oiint (i.e.
∬
\iint
∬
with a circle) but the command does not work on AoPS.
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