1. b) Find the rate of change of the area of a circle with respect to its radius r when
r = 4 cm
Area of the circle (A) =
Rate of change of the area of a circle with respect to its radius r = = =
So, when r = 4, Rate of change of the area of a circle = =
Hence, Rate of change of the area of a circle with respect to its radius r when r = 4 is