Correct answer: 1/2
The equation e^(cos² x + cos⁴ x + cos⁶ x +...) simplifies to a geometric series, which converges to a specific value. The roots of the quadratic equation t² - 9t + 8 = 0 are t = 1 and t = 8, and substituting these values leads to the correct trigonometric ratio, yielding the final answer of 1/2.