import hott.path tools.tactic

open path tactic
open path (induction_on)

definition concat_whisker2 {A} {x y z : A} (p p' : x ≈ y) (q q' : y ≈ z) (a : p ≈ p') (b : q ≈ q') :
  (whiskerR a q) ⬝ (whiskerL p' b) ≈ (whiskerL p b) ⬝ (whiskerR a q') :=
begin
  apply (induction_on b),
  apply (induction_on a),
  apply ((concat_1p _)⁻¹),
end