А = n-2/n × 180°
1) n = 3
a = 3-2/3 × 180° = 180°/3 = 60°
2) n = 4
a = 4-2/4 × 180° = 2/4 × 180° = 1/2 × 180° = 180°/2 = 90°
3) n = 5
a = 5-2/5 × 180° = 3/5 × 180° = 3 × 36° = 108°
4) n = 6
a = 6-2/6 × 180° = 4/6 × 180° = 4 × 30° = 120°
5) n = 10
a = 10-2/10 × 180° = 8/10 × 180° = 8 × 18° = 144°
6) n = 18
a = 18-2/18 × 180° = 16/18 × 180° = 16 × 10° = 160°