54. If Fe (n) is the Fourier cosine transform of f (x) on 0

Extracted text: 54. If Fe (n) is the Fourier cosine transform of f (x) on 0 < x="">< l,="" show="" that="" 2="" felf"="" (x)]="[(-1)"" f'="" (1)="" –="" f'="" (0)]="" –="" (4)*="" .="" (n).="" %3d="" when="" l="T," show="" that="" fels"="" (12))="[(-1)"" s'(7)="" –="" f'="" (0)]="" –="" n°f="" (n).="" [(-1)"="" f'="" (7)="" –="" f'="" (0)]="" –="" n²fc="">