Please sketch a proof for the following therom : If the point P is constructible from B, then the degree of the extension [ B(P) : B ] is some power of 2.
I have done a proof of this therom from the book Advanced abstract algebra by BHUPENDRA SINGH . But in this book the proof is given only for a special case where B(P) is considered as a field of real numbers and B is field of rationals. I am confused somewhere this therom includes a point P of plane ,and the proof is for a real number . Thanks.