Two high school students have a new proof of the Pythagorean Theorem / Pythag theorem older than thought

(I wrote this post a while back so its no longer NEW. More important--- if there has been a follow-up to the story that is not in my post, let me know.)  

 We have something NEW and something OLD about the Pythagorean Theorem. Now all we need is something BORROWED and something BLUE.

NEW

Two high school students have a new proof of the Pythagorean Theorem, see here.

They used trigonometry. Oh wait, that sounds circular since Trig is based on the Pythagorean Theorem. While this is a fair question to ask about the theorem, it has recently been accepted for publication and looked at carefully (those two are not equivalent) so it seems to be correct. 

The Pythagorean Theorem is an often-proved-theorem. Often an often-proved-theorem has proofs that use hard math (e.g., proofs that primes are infinite using Ramsey Theory, see my post on that here). However, the new proof of PT seems to be elementary. 

Kudos to them!

OLD:

Pythagorean theorem found on clay tablets1000 years earlier than Pythagoras: see here.

My students would ask me

 How come Pythagoras didn't go to arXiv to see if someone already had the theorem?