I have been working on a book/resource designed to transition learners' knowledge and skills with angles to trigonometry. A part of this is the Pythagoras theorem. A couple of years ago I developed the sheet below to promote discussion and thinking around the hypotenuse. It's rough, (I repeat - it's rough) but I have a new and improved version so the older conceptual model is below.
The idea is to just let people try to work out what needs to be done and how it might be done. Confusion is okay (avoid the need to explain it). This will lead to a conversation about Pythagoras - which presents an opportunity to play with the concept. Two versions below, the first with more scaffolding. Yes, they are rough - just concept stuff at this stage.
Would love to know if it works though!