Question 3 For an arbitrary function f define f* (z) = lim f ( z + h) - f(z - h) hot 2h if this limit exists. Let P be defined by cos(1/x) P(x) = if x # 0 if r = 0 and show that P*(0) = 0 even though P has no derivative at 0. (You must also show that P has no derivative at 0, but can assume that P is not continuous at 0 to do this.)