
theorem u3: 
for F being Field,
    E being FieldExtension of F
for a being F-algebraic Element of E 
for x being Element of F holds x = Ext_eval(x|F,a)
proof
let F be Field, E be FieldExtension of F;
let a be F-algebraic Element of E; let x be Element of F;
thus Ext_eval(x|F,a) = LC(x|F) by FIELD_6:28 .= x by RING_5:6;
end;
