幺矢量点积运算: e·i=e;=cOs6 .j=ei= sin 6 e=已 0 e, e2=COs 12=coS(02-81) e1·e"=-c0s(B2-6)cos cos( ) 1 2 = 1 2 = 2 −1 e  e   幺矢量点积运算： e  i = ei = cos   e  j = ej = sin   e  e = e 2 =1     = 0 t e e    = −1 n e e   ( ) 1 2 = − 2 −1  sin t e e   ( ) 1 2 = − 2 −1  cos n e e  