A student wishes to understand how the size of an angle (in radian) is connected to the length of the corresponding arc on a circle of radius r. Answer the following questions based on this situation:
(i) State the definition of one radian.
(ii) Using the definition stated in part (i), explain step by step why the numerical value of an angle θ (expressed in radian) is equal to the ratio of the arc length s to the radius r of the circle.
(iii) What specific value does θ take when the arc length equals the radius? Give a brief verbal interpretation of this result.