... vertex a line passes on which there lie at least 2 sides. Therefore, this 13-gon has not less than 3 + 2 · 6 = 15 sides but this is impossible. Figure 203 (Sol. 22.26) For n even, n ≥ 10, the ... AB and to each of them assign the number ±l, where l is the length of this side and the sine “plus” is taken if following this side in the direction of ray AB we get inside M and “minus” if we ... center at A 1 , where ∠A 2 A 1 A n < 90 ◦ and the n-gon A 1 . . . A n is a convex one, then for this n-gon there exist precisely n − 2 triangles required. 22.10. Proof will be carried out by induction...