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1973 USAMO
1
Two Points in Regular Tetrahedron
Two Points in Regular Tetrahedron
Source: 1973 USAMO Problem 1
March 7, 2010
geometry
3D geometry
tetrahedron
Problem Statement
Two points
P
P
P
and
Q
Q
Q
lie in the interior of a regular tetrahedron
A
B
C
D
ABCD
A
BC
D
. Prove that angle
P
A
Q
<
6
0
ā
PAQ < 60^\circ
P
A
Q
<
6
0
ā
.
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