S0=m()=4m() n, (t)cost=[n(t)cosat-n (t)sin a t]cos a z an(t)+ln(t)cos 2a t-n(t)sin atl 2 ()1 n()N=n2(t) 1n2(t) N=1n()=1N 2(t B 44 n t t n t t n t t t i  c c  c s  c  c ( )cos =[ ( )cos − ( )sin ]cos [ ( )cos2 ( )sin 2 ] 2 1 ( ) 2 1 n t n t t n t t = c + c  c − s  c ( ) 2 1 ( ) 0 n t n t  = c ( ) 4 1 ( ) 2 2 0 0 N n t n t = = c i Ni N n t 4 1 ( ) 4 1 2 0 = = n B m t N S i i 0 2 ( ) 2 1 = ( ) 4 1 ( ) 2 2 0 0 S = m t = m t