Suppose \( \theta\in\left[0,\dfrac{\pi}{4}\right] \) is a solution of \( 4\cos\theta-3\sin\theta=1 \). Then \( \cos\theta \) is equal to:
\( \dfrac{4}{3\sqrt{6}+2} \)
\( \dfrac{6+\sqrt{6}}{3\sqrt{6}+2} \)
\( \dfrac{6-\sqrt{6}}{3\sqrt{6}-2} \)
\( \dfrac{4}{3\sqrt{6}-2} \)