The period of \( \sin A \cos A \) is given by \( \frac{2\pi}{|A|} \). Here, \( A = 4x \), so the period of \( 2 \sin 4x \cos 4x \) is: \[ \frac{2\pi}{4} = \frac{\pi}{4} \] Thus, the correct answer is \( \frac{\pi}{4} \).