0000:00:00:00:00Start18Number 18ExplanationThe solution set of the trigonometric equation cos2x−2cosx=−1\cos 2x - 2\cos x = -1cos2x−2cosx=−1 for 0≤x≤2π0 \leq x \leq 2\pi0≤x≤2π is ....{0,12π,π}\left\{0, \frac{1}{2}\pi, \pi\right\}{0,21π,π}{0,12π,23π}\left\{0, \frac{1}{2}\pi, \frac{2}{3}\pi\right\}{0,21π,32π}{0,12π,π,32π}\left\{0, \frac{1}{2}\pi, \pi, \frac{3}{2}\pi\right\}{0,21π,π,23π}{0,12π,23π,2π}\left\{0, \frac{1}{2}\pi, \frac{2}{3}\pi, 2\pi\right\}{0,21π,32π,2π}{0,12π,32π,2π}\left\{0, \frac{1}{2}\pi, \frac{3}{2}\pi, 2\pi\right\}{0,21π,23π,2π}
18Number 18ExplanationThe solution set of the trigonometric equation cos2x−2cosx=−1\cos 2x - 2\cos x = -1cos2x−2cosx=−1 for 0≤x≤2π0 \leq x \leq 2\pi0≤x≤2π is ....{0,12π,π}\left\{0, \frac{1}{2}\pi, \pi\right\}{0,21π,π}{0,12π,23π}\left\{0, \frac{1}{2}\pi, \frac{2}{3}\pi\right\}{0,21π,32π}{0,12π,π,32π}\left\{0, \frac{1}{2}\pi, \pi, \frac{3}{2}\pi\right\}{0,21π,π,23π}{0,12π,23π,2π}\left\{0, \frac{1}{2}\pi, \frac{2}{3}\pi, 2\pi\right\}{0,21π,32π,2π}{0,12π,32π,2π}\left\{0, \frac{1}{2}\pi, \frac{3}{2}\pi, 2\pi\right\}{0,21π,23π,2π}
