let V be RealLinearSpace; for x, y being VECTOR of V st Gen x,y holds
CMSpace (V,x,y) is Oriented_Orthogonality_Space
let x, y be VECTOR of V; ( Gen x,y implies CMSpace (V,x,y) is Oriented_Orthogonality_Space )
assume A1:
Gen x,y
; CMSpace (V,x,y) is Oriented_Orthogonality_Space
then A2:
for u, v, w being Element of (CMSpace (V,x,y)) ex u1 being Element of (CMSpace (V,x,y)) st
( w <> u1 & w,u1 '//' u,v )
by Th2;
A3:
for u, v, w being Element of (CMSpace (V,x,y)) ex u1 being Element of (CMSpace (V,x,y)) st
( w <> u1 & u,v '//' w,u1 )
by A1, Th2;
for u, u1, v, v1, w, w1, w2 being Element of (CMSpace (V,x,y)) holds
( u,u '//' v,w & u,v '//' w,w & ( u,v '//' u1,v1 & u,v '//' v1,u1 & not u = v implies u1 = v1 ) & ( u,v '//' u1,v1 & u,v '//' u1,w & not u,v '//' v1,w implies u,v '//' w,v1 ) & ( u,v '//' u1,v1 implies v,u '//' v1,u1 ) & ( u,v '//' u1,v1 & u,v '//' v1,w implies u,v '//' u1,w ) & ( not u,u1 '//' v,v1 or v,v1 '//' u,u1 or v,v1 '//' u1,u ) )
by A1, Th2;
hence
CMSpace (V,x,y) is Oriented_Orthogonality_Space
by A2, A3, Def1; verum