Question

If the central angle is 4pi/3 radians, what should the radius of a circle be to make the arc length 1 m?


a) 0.424 m

b) 0.238 m

c) 2.356 m

d) 4.188 m

I think it is c)... is that correct?

Answer 1

s = rθ, so
r * 4π/3 = 1, so
r = 3π/4 = 2.356
C is correct

Answer 2

4pi/3 radians = 4*180/3 = 240 degrees.
(240/360)C = 2C/3 = 1 meter.
(2/3)3.14*2r = 1
r = 0.2387 m.

Answer 3

s=theta*r
Given s=1cm and theta =4pi/3
Therefore :
1cm=4pi/3*r

Multiply both sides by 3/4pi to make r subject of the formula.

3/4pi*1cm=3/4pi *4/3pi *r
Therefore r =3pi/4

Plug that in your calculator to see which of the answers correspond..