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Problem
Problem
Let
n
n
n
be positive integer such that
sin
π
2
n
+
cos
π
2
n
=
n
2
\sin \frac{\pi}{2n} + \cos \frac{\pi}{2n} = \frac{\sqrt{n}}{2}
sin
2
n
π
+
cos
2
n
π
=
2
n
. Then a.
6
≤
n
≤
8
6 \le n \le 8
6
≤
n
≤
8
b.
4
<
n
≤
8
4 < n \le 8
4
<
n
≤
8
c.
6
<
n
<
8
6 < n < 8
6
<
n
<
8
d.
4
<
n
<
8
4 < n < 8
4
<
n
<
8
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