more math proofreading

[redbird]

I would further like to note that an isoceles right triangle cannot have sides all of whose lengths are a whole number of units, and that whoever edited that manuscript should have noticed that 20:20:24 isn't even close to the right value of the hypotenuse. Since the point of the example is naming shapes of triangles, not the Pythagorean theorem, and they haven't had irrationals or the Pythagorean theorem yet, it got a suggested change to 28 (the closest integer to the actual value), and a note that we can't avoid irrationals, with the shorthand explanation "(1:1:√2)". I haven't handed it in yet, and am now wondering whether it would be better not to give a length for the hypotenuse. The editor on this project may know their pedagogy, but they're not sufficiently intimate with numbers.