(8)(A×B)xC=B(AoC)-A(B·C)=e12-e40 Ax(B×C)=B(A·C)-C(AB)=e15-e44-2e11 1.2A12=e14+e10-eA3=e2+e1+8 A3=-216-e-e7A12·A3=0 S==A 12 A23=1712 1.3A 5-e3 PP 144=√29B=√77AB=-31COS0= A●B 0.65 AB 6=180-49=1314CO9=√29(0656)=-353312 23 (8) ( ) ( ) ( ) 2 40 ( ) ( ) ( ) 55 44 11... 1.2 4 0 2 8 x y x y z x y z x y z A B C B A C A B C e e A B C B A C C A B e e e A e e e A e e e A   = • − • = −   = • − • = − − = + − = + + ' 13 12 23 12 23 6 7 0 1 17.12 2 1.3 5 3 . 1.4 29 77 31 0.656 180 49 131 x y z P P x y z A e e e A A S A A A A e e e e A A B A B A B COS AB   = − − − • = =  = = − − = • = = • = − = = − = − = 0 . 29 ( 0.656) 3.533 ACOS =  − = −