Similarly we =y Here we prove the relation of the equality get of cross shears again fom∑x=0∑r=0∑Z=0 + +X=0 Ox List the equations. cancel terms we get +Y=0 These are differential equations of equilibrium a0 Otx+S under rectangular coordinate of space Ov+Z=0 Two. Geometric Equations For spatial problems, deformation components and displacement components should satisfy following geometric equations Ow Oy L OW y O 8= Ov au y Of which the first two and the last have been obtained among plane problems, the other three can be led out with the same method 99 xy yx zx xz yz zy       = = = Similarly,we get Here we prove the relation of the equality of cross shears again from X = 0,Y = 0,Z = 0 List the equations,cancel terms,we get These are differential equations of equilibrium under rectangular coordinate of space          + =   +   +   + =   +   +   + =   +   +   0 0 0 Z z x y Y y z x X x y z z xz yz y z y xy x yx z x          Two. Geometric Equations For spatial problems, deformation components and displacement components should satisfy following geometric equations z w y v x u z y x   =   =   =    y u x v x w z u z v y w xy zx yz   +   =   +   =   +   =    Of which the first two and the last have been obtained among plane problems, the other three can be led out with the same method