Answer:
1/6
Step-by-step explanation:
The circumference of a circle is denoted by: 
 , where r is the radius. Here, r = 1, so plug this in:
, where r is the radius. Here, r = 1, so plug this in:

 units
 units
Now, we know that arc AB has a length of 
 and we want to find the fraction of the circumference this is. So, divide
 and we want to find the fraction of the circumference this is. So, divide 
 by
 by 
 :
:

Thus, the fraction is 1/6.
Hope this helps!