How can you see in this picture
of what order the covering maps be? Well I look for one with a degree of two and one with a degree of four. thanks a lot!
How can you see in this picture
of what order the covering maps be? Well I look for one with a degree of two and one with a degree of four. thanks a lot!
Count vertices. [And forget about the rest: $a,b, a^2,a^{-1},...$]
These are covering spaces for $S^1\vee S^1$. The edges labeled '$a$' map to one of the $S^1$'s and the edges labeled '$b$' map to the other. You only need to count the number of occurrences of '$a$', or '$b$'. For example, $(1)$ has two $a$'s and two $b$'s and is thus a double cover.