I am in need of help solving this problem. I got the missing side as sqrt (34), but that all I've got.

And this is kind of separate from this problem, but I don't really understand the Pythagorean Theorem with these problems. This one made sense, but another one I did had 40 as the hypotenus, and 41 as the opposite. I had to find "c". Well, I ended up with a=sqrt(40^2-41^2), because that makes sense, right? It turned out to be 41^2-40^2, but how? Wouldn't that have been sqrt(-41^2+40^2) if written the other way? I took a^2+b^2=c^2 and solved for "a". Is this not correct? I'm very confused, and any help would be appreciated! But the main focus of this thread is in my attachment.

I didn't know how to write those characters so I drew up the problem.