6. Show that on (7r,7r), accos(:1:) = % sin(:r:) | 2 (% sin(2:1:) % sin(3:1:) | % sin(4:1:) - - ) , and then showing the needed intermediate steps in your analysis use this series to derive the Fourier cosine series of the function f (:3) = :rsin(:1:) on 7r