* (a) lie in an extension of the rationals of degree 2^n; (b) be algebraic, in the sense that its coordinates are roots of rational polynomials.* (a) implies (

* (a) lie in an extension of the rationals of degree 2^n; (b) be algebraic, in the sense that its coordinates are roots of rational polynomials.* (a) implies (b) here, but I’m sure you know this. From myself, I recommend Aluffi’s “Algebra. Chapter 0”, it’s more modern and I find its style much more matching my taste.