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Novosibirsk Oral Olympiad in Geometry
2017 Novosibirsk Oral Olympiad in Geometry
2
<CDB? <CAD=<DBA=40,<CAB=60,<CBD=20 (2017 Novosibirsk Oral Geo Oly 8-9 p2)
<CDB? <CAD=<DBA=40,<CAB=60,<CBD=20 (2017 Novosibirsk Oral Geo Oly 8-9 p2)
Source:
April 26, 2021
geometry
angles
Problem Statement
You are given a convex quadrilateral
A
B
C
D
ABCD
A
BC
D
. It is known that
∠
C
A
D
=
∠
D
B
A
=
4
0
o
\angle CAD = \angle DBA = 40^o
∠
C
A
D
=
∠
D
B
A
=
4
0
o
,
∠
C
A
B
=
6
0
o
\angle CAB = 60^o
∠
C
A
B
=
6
0
o
,
∠
C
B
D
=
2
0
o
\angle CBD = 20^o
∠
CB
D
=
2
0
o
. Find the angle
∠
C
D
B
\angle CDB
∠
C
D
B
.
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