Let \( f : \mathbb{R} \to \mathbb{R} \) be a continuous function. Then $\displaystyle \lim_{x \to \frac{\pi}{4}} \frac{\frac{\pi}{4} \int_{2}^{\sec^2 x} f(x) \, dx}{x^2 - \frac{\pi^2}{16}}$ is equal to:
\( 2\,f(\sqrt{2}) \)
\( 2\,f(2) \)
\( 4\,f(2) \)
\( f(2) \)