思考题解答 (p(x)cos ndx T C- op(-t)cos(-nt)d(t cp(x)cos ndx 几=兀 EY(x)cos ndx (n=0,1,2,…)思考题解答   −   an = (x)cos nxdx 1  −   − − −  = ( )cos( ) ( ) 1 t nt d t   −  −  = ( x)cos nxdx 1   −   = (x)cos nxdx 1 (n = 0,1,2, )