English
If natDegree p < natDegree q then degree p < degree q.
Русский
Если natDegree p < natDegree q, то degree p < degree q.
LaTeX
$$$ p, q \in R[X], p \neq 0 \Rightarrow [\operatorname{natDegree}(p) < \operatorname{natDegree}(q) \Rightarrow \deg(p) < \deg(q)] $$$
Lean4
theorem degree_lt_degree (h : natDegree p < natDegree q) : degree p < degree q :=
by
by_cases hp : p = 0
· simp only [hp, degree_zero]
rw [bot_lt_iff_ne_bot]
intro hq
simp [hp, degree_eq_bot.mp hq] at h
· rwa [degree_eq_natDegree hp, degree_eq_natDegree <| ne_zero_of_natDegree_gt h, Nat.cast_lt]