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Iran MO (2nd Round)
1985 Iran MO (2nd round)
3
Find the angle - [Iran Second Round 1985]
Find the angle - [Iran Second Round 1985]
Source:
December 29, 2010
geometry
3D geometry
vector
trigonometry
algebra proposed
algebra
Problem Statement
Find the angle between two common sections of the page
2
x
+
y
−
z
=
0
2x+y-z=0
2
x
+
y
−
z
=
0
and the cone
4
x
2
−
y
2
+
3
z
2
=
0.
4x^2-y^2+3z^2=0.
4
x
2
−
y
2
+
3
z
2
=
0.
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