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2011 LMT
11
2011 Spring LMT Individual Round Problem 11
2011 Spring LMT Individual Round Problem 11
Source:
January 5, 2021
Problem Statement
Let
A
B
C
D
ABCD
A
BC
D
be a convex quadrilateral with
A
B
=
A
D
,
m
∠
A
=
4
0
∘
,
m
∠
C
=
13
0
∘
,
AB=AD, m\angle A = 40^{\circ}, m\angle C = 130^{\circ},
A
B
=
A
D
,
m
∠
A
=
4
0
∘
,
m
∠
C
=
13
0
∘
,
and
m
∠
A
D
C
−
m
∠
A
B
C
=
2
0
∘
.
m\angle ADC - m\angle ABC = 20^{\circ}.
m
∠
A
D
C
−
m
∠
A
BC
=
2
0
∘
.
Find the measure of the non-reflex angle
∠
C
D
B
\angle CDB
∠
C
D
B
in degrees.
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