1. Show that formally Assume that a function f has a Fourier series nx L f(x) = by sin n=1 [*Pr=[% L 2. Is there a corresponding result if f has a cosine series? explain and justify your answer 3. Apply the result of part (1) to the series for the sawtooth function f, and therefore show that 77 6 2 = 1+ 1 1 22 32 0xL + 1 n 71=1 where f is given by f(x) = x, -L < x < L, and f(-L) = f(L) = 0 and f is 2L periodic, that is f(x+2L) = f(x).