nπ+(−1)nπ6n \pi+(-1)^{n} \frac{\pi}{6}nπ+(−1)n6π
13nπ+π6\frac{1}{3} n \pi+\frac{\pi}{6}31nπ+6π
13nπ+(−1)nπ6\frac{1}{3} n \pi+(-1)^{n} \frac{\pi}{6}31nπ+(−1)n6π
13nπ+(−1)nπ18\frac{1}{3} \mathrm{n} \pi+(-1)^{\mathrm{n}} \frac{\pi}{18}31nπ+(−1)n18π