Let be a positive integer such that

MATHEMATICS · Multi correct · A Level · Mathematics · Trigonometry · Trigonometry

Problem

Let

n

be a positive integer such that

\sin\frac{\pi}{2n}+\cos\frac{\pi}{2n}=\frac{\sqrt{n}}{2}

. Then: (1)

6\leq n\leq8

(2)

4<n\leq8

(3)

6<n<8

(4)

4<n<8