Question

For the problem below, θ is a central angle in a circle of a radius r. Find the length of arc s cut off by θ.

( look at pictures for more information

Answer 1

Here, we will use the formula from trigonometry which defines a radian

we know that an angle is a radian when the length of the radius of the circle is equal to the length of the arc formed

hence, if the radius is r and the arc is r, the angle (in radians) will be 1

if the radius is r and the arc is 2r, the angle in radians will be equal to:

length of arc / radius = 2r/r = 2 radians

I believe this will explain what is actually happening in these type of questions

So, the equation:

Θ(in radians) = s / r (where the length of arc is s and the radius is r)

π/4 = s / 12

s = 3π or 9.42 inches