Appendix A Solutions t o the Exercises 515
7 l h) A ( j 0 ) = -
c) 7'1ie first zcro of the aperlure furicfion should be at half the saiiiple freqiiency
the argument o l Ihe si fiinct,ion should be equal t o 7r
The first zero of'the si trrrii IS a t
7r
The ros term has peiiotl U+, = - -+ SO = 72 H a Accordingly the zcros of the
term in square hrackcts arc at 24 r, Hz and 48 Hz