Let x0 of type ι be given.
Apply Field_minus_eq with
x0,
field4 x0,
λ x1 x2 . field2b x0 x2 x2 = field4 x0 leaving 3 subgoals.
The subproof is completed by applying H0.
Apply Field_one_In with
x0.
The subproof is completed by applying H0.
Apply explicit_Field_minus_one_square with
field0 x0,
field3 x0,
field4 x0,
field1b x0,
field2b x0.
Apply Field_explicit_Field with
x0.
The subproof is completed by applying H0.