A stone is dropped into a lake, creating a circular ripple that travels outward at a speed of 20 cm/s. Find the rate at Which the area within the circle is increasing after: (a) 1 s (b) 3 s (c) 5 5 (What can can you conclude?) (a) 3', sq cm/sec (b) 9', sq cm/sec If R denotes the reaction of the body to some stimulus of strength x, the sensitivity 5' is dened to be the rate of change of the reaction with respect to m. A particular example is that when the brightness as of a light source is increased, the eye reacts by 40 24$\" 1 4 0 4 has been used to model the dependence of R __ a; . decreasing the area R of the pupil. The experimental formula R(x) = on a: when R is measured in sq mm and a: is measured in the appropriate units of brightness. Find the sensitivity. R'(a:) = i. A