ANSWER:
[tex]x=\frac{\pi}{3}, \frac{5\pi}{3}[/tex]
STEP-BY-STEP EXPLANATION:
W have the following equation:
[tex]\cos x-1=-\cos x[/tex]
We solve for x:
[tex]\begin{gathered} \cos x-1=-\cos x \\ \\ \cos x=u \\ \\ u-1=-u \\ \\ u+u-1=0 \\ \\ 2u=1 \\ \\ u=\frac{1}{2} \\ \\ \cos x=\frac{1}{2} \\ \\ x=\frac{\pi}{3},\frac{5\pi}{3} \end{gathered}[/tex]
