theorem :: ALGSTR_3:4

for F being Ternary-Field
for a, a9, u, u9, v, v9 being Scalar of F st a <> a9 & Tern (u,a,v) = Tern (u9,a,v9) & Tern (u,a9,v) = Tern (u9,a9,v9) holds
( u = u9 & v = v9 )