类似地 (Ao)y cosa>0 (△S)z=1-(△o)yzc0sa<0 cosa=0 (△a)x2C0s>0 (△S)x2={-(△ xz C0S<0 0 cos B=0 K心类似地 ; 0 cos 0 ( ) cos 0 ( ) cos 0 ( )      = −      =      yz yz S yz . 0 cos 0 ( ) cos 0 ( ) cos 0 ( )      = −      =      x z x z S x z