For the following trigonometric equation written in quadratic form, use algebraic techniques to solve in the interval [0, 2π) and give the answer in radians.
14 cos² A - 7cos A - 7 = 0

• A. A = {0, 2π/3, 4π/3}
• B. A = {0, 3π/4, 5π/4, 3π/2}
• C. A = {0, 5π/6, 7π/6}
• D. A = {0, π/4, 3π/2, 7π/4}

Answer: (A)