2) Double Cross (A×B)×(C×D)orA/B/C/D (A×B)×(A×C)orA/B∥AC(A=12) 3) Tetra cross A/B/C/3/D(D=1/2) 4)Convergent Cross A/B/CD/3/E/F∥G/H2）Double Cross (A×B)×(C×D) or A/B//C/D (A×B)×(A×C) or A/B//A/C (A=1/2) 3）Tetra Cross A/B//C/3/D (D=1/2) 4) Convergent Cross A/B//C/D /3/ E/F//G/H