Simplify the following: x - 3 x2

Answer: Option C

$$\begin{array}{rl}& \frac{\cos x-\sqrt{3}\sin x}{2}\\ & \Rightarrow \frac{1}{2}\cos x-\frac{\sqrt{3}}{2}\sin x\\ & \Rightarrow \cos 60^{\circ }.\cos x-\sin 60^{\circ }.\sin x\\ & \Rightarrow \cos \left({60}^{\circ }+x\right)\\ & \Rightarrow \cos \left(\frac{\pi }{3}+x\right)\end{array}$$