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Mathematics
Mathematics
Problem
A cyclic quadrilateral
A
B
C
D
ABCD
A
B
C
D
is inscribed in a circle. The side lengths are
A
B
=
2
AB = 2
A
B
=
2
,
B
C
=
3
BC = 3
B
C
=
3
,
C
D
=
4
CD = 4
C
D
=
4
, and
D
A
=
5
DA = 5
D
A
=
5
. Using the property that opposite angles sum to
180
∘
180^{\circ}
18
0
∘
, find the cosine of
∠
B
\angle B
∠
B
.
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