Set: pp::colors
  Set: pp::unicode
  Assumed: f
  Assumed: g
  Assumed: Axf1
  Assumed: Axfg
  Assumed: a
  Assumed: b
Axfg : ∀ x : ℕ, g x x = x
Axf1 : ∀ x : ℕ, f (f x) = x
a	trans (congr2 (g a) (Axf1 a)) (Axfg a)
g a a	congr2 (g a) (Axf1 a)
a	trans (congr2 (g a) (Axf1 a)) (Axfg a)
a	trans (congr2 (g a) (Axf1 a)) (Axfg a)