How to obtain t-o curve F cos a ocos。cos cOS sin< n coS poL Ln=·n→ Lcos o=lcos1L_ cos o sin n Lxb=1×b→Lsin=lsn COS .T=OCOS o sin-aHow to obtain curve  −       = − − = =                ( ) sin cos cos 1 cos cos cos cos 2 2 l L A F ① ②               sin sin cos cos L b l b L l L n l n L l  =   =  =   =     sin sin cos cos    = = l L ③     2 2 cos 1 ( ) sin l L  = − ④