Q63. Suppose $\theta \epsilon \left[ 0 , \frac { \pi } { 4 } \right]$ is a solution of $4 \cos \theta - 3 \sin \theta = 1$. Then $\cos \theta$ is equal to :\\
(1) $\frac { 4 } { ( 3 \sqrt { 6 } + 2 ) }$\\
(2) $\frac { 6 + \sqrt { 6 } } { ( 3 \sqrt { 6 } + 2 ) }$\\
(3) $\frac { 4 } { ( 3 \sqrt { 6 } - 2 ) }$\\
(4) $\frac { 6 - \sqrt { 6 } } { ( 3 \sqrt { 6 } - 2 ) }$