71 4. The terminal arm of an angle 0, drawn in standard position, intersects a circle with radius r a point A. (7 marks - Thinking) a) Draw a diagram to illustrate the problem and state the coordinates of A, as a function of r and 9. [2] b) Determine the area of the right triangle formed by the origin, point A, and the point on the x-axis directly below A, as a function of r and 0. [2] c) Determine the value of 0 that produces the triangle of greatest area, given that r = 4 and 0