Sum ∑_{k=1}^{n} cos(kθ).

Sum ∑_{k=1}^{n} cos(kθ).

A [sin(nθ/2) cos((n + 1)θ/2)] / sin(θ/2)

B [sin((n + 1)θ/2) cos(nθ/2)] / sin(θ/2)

C [sin(nθ) cos(θ)] / sin(θ)

D [sin(nθ/2) sin((n + 1)θ/2)] / sin(θ/2)

Solution

Correct Answer: Option B