> They probably didn't have the modern form we use where plugging in different values like 1 is a natural and obvious thing to do. No, but the form they used w

> They probably didn't have the modern form we use where plugging in different values like 1 is a natural and obvious thing to do. No, but the form they used was that they thought about lines in a plane that had no particular scale other than whatever you might assign to them. "Plugging in 1" for the sides of a right triangle in that model just means that you look at an isosceles right triangle. It will always be obvious.