If $$\cos \theta + \sin \theta = \sqrt{2} \cos \theta$$, find the value of $$\left(\cos \theta - \sin \theta\right)$$.

A

$$\sqrt{2} \sin \theta$$

B

$$\sqrt{2} \cos \theta$$

C

$$\frac{1}{\surd{2}} \sin \theta$$

D

$$\frac{1}{2} \cos \theta$$