4. An n-periodic function is a function such that f(2) = f(r + n) for some value of n. Let f(z) be a continuous n-periodic function. (i) Show that for any whole number k, cos(x )dr = 0. (ii) Suppose that the anti-derivative of f. F is also n-periodic. Show that for any whole number k. f(x)de = 0. Justify your response. (iii) Explain how part (ii) relates to part (i)