Apply CD_mul_proj1 with
Sing 2,
SNo,
minus_SNo,
λ x0 . x0,
add_SNo,
mul_SNo leaving 5 subgoals.
The subproof is completed by applying complex_tag_fresh.
The subproof is completed by applying SNo_minus_SNo.
Let x0 of type ι be given.
The subproof is completed by applying H0.
The subproof is completed by applying SNo_add_SNo.
The subproof is completed by applying SNo_mul_SNo.