Answer:
Ф = s/r
Explanation:
The arc length formula is s = rФ, where r is the radius and Ф is the central angle. We want to find a formula for the angle Ф in terms of s and r. To do this, start with s = rФ and divide both sides by r:
s rФ
-- = ----
r r
Then Ф = s/r