MathDB

The vertices of a regular

4

-gon,

6

-gon and

12

-goncan be brought together in one point to form a complete angle of

360^o

(see figure). https://cdn.artofproblemsolving.com/attachments/b/1/e9245179b7e0f5acb98b226bdc6db87fd72ad5.png Determine all triples

a, b, c \in N

with

a < b < c

for which the angles of a regular

a

-gon,

b

-gon and

c

-gon together also form

360^o

3