由于递推关系 21+111 0 a IP1(x)-P1(x)=[P1(x)-P1(x) 2 2 cos a dcos a 2 7-(cos a)-P+(cos ax =0 sin 0d0=-(1-cos a) U l(r,)==(1-cosa)+ 2 2 LIP- (cos a)-P+ (cos ax)1-P(cos 0)由于递推关系： [ ' '] 2 1 1 1  1  l  Pl Pl l P P x P x dx U A a l l a l l [ '( ) '( )] 2 1 1 1 cos      1 1 1 cos [ ( ) ( )] 2 l l a P x P x U     [ (cos ) (cos )] 2 1 1 P a P ax U  l  l l  0 l  0 (1 cos ) 2 sin 2 0 0 a U d U A a       [ (cos ) (cos )] (cos ) 2 (1 cos ) 2 ( , ) 1  1 1 l  l l l l l P a r P a P ax U a U u r         