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Mathematics
Mathematics
Problem
Lines
A
B
AB
A
B
and
C
D
CD
C
D
intersect at
O
O
O
, forming four angles named
∠
A
O
C
\angle AOC
∠
A
O
C
,
∠
C
O
B
\angle COB
∠
C
O
B
,
∠
B
O
D
\angle BOD
∠
B
O
D
and
∠
D
O
A
\angle DOA
∠
D
O
A
. Which one of the following angles is equal to
∠
A
O
C
\angle AOC
∠
A
O
C
? a)
∠
C
O
B
\angle COB
∠
C
O
B
b)
∠
B
O
D
\angle BOD
∠
B
O
D
c)
∠
D
O
A
\angle DOA
∠
D
O
A
d)
∠
A
O
B
\angle AOB
∠
A
O
B
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