geometry
posted by matt .
Given a circle with the radius of 2, which is the degree measure of an arc whose length is 1/2 pi?

arclength = rß where ß is in radians
pi/2 = 2ß
ß= pi/4 radians, which is 45 degrees
or
the whole circumference would be 2(pi)r
= 4pi
now by a simple ratio ....
(1/2)pi/(4pi) = angle/360
4angle = 180
angle = 45