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If 2tan 2 θ – 5sec θ = 1 has exactly 7 solutions in the interval ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ π 2 n , 0 , for the least value of n ∈ N, then ∑ = n 1 k k 2 k is equal to:

1. 1 – 13 2 15
2. 13 2 1 (2 14 – 15)
3. 14 2 1 (2 15 – 15)
4. 15 2 1 (2 14 – 14)

Correct answer: 13 2 1 (2 14 – 15)

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