Let x0 of type ι be given.
Apply nat_ind with
λ x1 . nat_p (add_nat x0 x1) leaving 2 subgoals.
Apply add_nat_0R with
x0,
λ x1 x2 . nat_p x2.
The subproof is completed by applying H0.
Let x1 of type ι be given.
Apply add_nat_SR with
x0,
x1,
λ x2 x3 . nat_p x3 leaving 2 subgoals.
The subproof is completed by applying H1.
Apply nat_ordsucc with
add_nat x0 x1.
The subproof is completed by applying H2.