4. Consider the function f(x) = sin ((@) |. (a) (6 points) Compute the Fourier coefficient a, for this function. (b) (6 points) Use a right-hand Riemann sum with 4 rectangles to approximate the Fourier coefficient a, for this function. (c) (2 points) Explain why be must be zero for all k. (d) The Fourier series for f(r) is = + 4 TT (1 - 4k2) cos (kI). k=1 i. (6 points) Graph the Fourier series of f (x) on [-4x, 4x]. ii. (6 points) Use this to find the sum of 1 1 - 412 K=1