Im doing a problem for al algorithms class to multiply 2 polynomials using FFT, and am confused as to why they picked 9 in step 3 in this document: http://www.cc.gatech.edu/~venkat/6505/notes/fftex.pdf
Which means the last piece of the puzzle im missing is how i can find the principal N-th root of unity for any 2 arbitrarily chosen polynomials. (in my case, they are 1+x+2x^2 and 2+3x)