So I fell behind in my last semester geometry class, so right now I’m working with Pythagorean Triples. Here’s the screenshot of the work I’m doing and I’m confused on what “DEF” is? I drew my vertices for “ABC” but then it starts talking about measurements etc.

So I fell behind in my last semester geometry class so right now Im working with Pythagorean Triples Heres the screenshot of the work Im doing and Im confused o class=