Answer the following questions with respect to a circle.
a. (i) Define a central angle and an inscribed angle of a circle.
b. (ii) State and explain the relationship between the measure of a central angle and the measure of an inscribed angle subtended by the same arc.
c. (iii) Let AB be a diameter of a circle and C be any point on the circle different from A and B. Using the result of part (ii), show that △ACB is a right-angled triangle.