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Problems
Let
A
=
{
θ
∈
(
0
,
2
π
)
:
1
+
2
i
sin
θ
1
−
i
sin
θ
is purely imaginary
}
.
A = \left\{ \theta \in (0, 2\pi) : \frac{1+2i \sin \theta}{1-i \sin \theta} \text{ is purely imaginary} \right\}.
A
=
{
θ
∈
(
0
,
2
π
)
:
1
−
i
sin
θ
1
+
2
i
sin
θ
is purely imaginary
}
.
…
Mathematics
Problem
Let
A
=
{
θ
∈
(
0
,
2
π
)
:
1
+
2
i
sin
θ
1
−
i
sin
θ
is purely imaginary
}
.
A = \left\{ \theta \in (0, 2\pi) : \frac{1+2i \sin \theta}{1-i \sin \theta} \text{ is purely imaginary} \right\}.
A
=
{
θ
∈
(
0
,
2
π
)
:
1
−
i
sin
θ
1
+
2
i
sin
θ
is purely imaginary
}
.
Then, the sum of the elements in
A
A
A
is (2023 Main, 8 April II) (a)
2
π
2\pi
2
π
(b)
3
π
3\pi
3
π
(b)
π
\pi
π
(d)
4
π
4\pi
4
π
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