OK, with that in mind, let's revisit the type of the function we want to write: forall (l1 l2 : list T), length l1 = m -> length l2 = n -> length (append l1 l2) = m + n What does it do? Well, it will take in two lists as arguments. So let's modus ponens that shit.

Thank you SO much, Margaret Lake (and Margaret’s Granny!)…embroidered lab coat might just be the best win so far….not to mention the amazing job Margaret Lake did on her first surgeries today!! Super proud and grateful!!🎉🤓🥰❤️