whats the radius if the arc length is 40cm and the central angle is 20 degrees
+227 
Well, this is just plain solving equations. From your problem, s=40 and θ=20°. Never mind, you need to know how to make degrees radians. To do this, just use a proportion:degreesradians=180pi
You have degrees, so just plug stuff in and cross multiply. This gives you 20π=180*(x radians). (x is what we're solving for.) Solving gives x= π/9 radians.
Now we know θ in terms of radians. We can just plug our numbers in and solve!
40=r(π/9)
Divide by π/9 to get r=360/π cm!
EDIT: CPhill pointed out to me that I had made a mistake: 40*9=360, not 540 as I had put earlier.
+227
Well, this is just plain solving equations. From your problem, s=40 and θ=20°. Never mind, you need to know how to make degrees radians. To do this, just use a proportion:degreesradians=180pi
You have degrees, so just plug stuff in and cross multiply. This gives you 20π=180*(x radians). (x is what we're solving for.) Solving gives x= π/9 radians.
Now we know θ in terms of radians. We can just plug our numbers in and solve!
40=r(π/9)
Divide by π/9 to get r=360/π cm!
EDIT: CPhill pointed out to me that I had made a mistake: 40*9=360, not 540 as I had put earlier.
