Question

The central angle of a circle is equal in measure to one radian when the corresponding arc length is equal to which of the following? A) The radius of the circle B) Any chord of the circle C) The diameter of the circle D) One-half the circumference of the circle

Answer 1

The formula to find the arc length L is
L = r*theta
where r is the radius and theta is the central angle in radians (this formula will not work if theta is in degrees)

If the central angle is 1 radian, then theta = 1 and
L = r*theta
L = r*1
L = r
So the arc length is the same as the radius

Answer: Choice A) The radius of the circle

Answer 2

Arc length = radius * central angle in radians
answer is A

Source:
http://www.1728.org/radians.htm