Algebra 2 (1st Edition)

$x=4 n \pi$
Here, we have $\cos \dfrac{x}{2}=1$ It has to be noted that when $\cos \dfrac{x}{2} =\cos 0$ The general solution for $\cos \theta=\cos \alpha$ is $\theta=2 n \pi \pm \alpha$ Now, we find that the general solution for $\cos (x/2)=\cos (0)$ is $(x/2)=2 n \pi \pm (0)$ This gives: $\dfrac{x}{2}=2 n \pi$ Hence, we have $x=4 n \pi$