how to find arc length

Question

the radius is 12 and theta is pi over two how do i find the arc length

Answer 1

6pi

arc length = radius times radians = 12(pi/2) = 6pi

or another way of looking at it is pi/2 is one quarter of the circle, so arc length = 1/4 of the circumference. circumference = 2rpi = 2(12)pi = 24pi, divide by 4,

24pi/4 = 6pi