There is no equation here
Answer:
(a). The path length is 3.09 m at 30°.
(b). The path length is 188.4 m at 30 rad.
(c). The path length is 1111.5 m at 30 rev.
Explanation:
Given that,
Radius = 5.9 m
(a). Angle 
We need to calculate the angle in radian

We need to calculate the path length
Using formula of path length



(b). Angle = 30 rad
We need to calculate the path length


(c). Angle = 30 rev
We need to calculate the angle in rad


We need to calculate the path length


Hence, (a). The path length is 3.09 m at 30°.
(b). The path length is 188.4 m at 30 rad.
(c). The path length is 1111.5 m at 30 rev.
And.. where is the rest of the question?
Given :
Current, I = 3.75 A .
Magnetic Field, 
To Find :
The distance from the wire.
Solution :
We know,

Hence, this is the required solution.