det P = t**2 + t + 1
Lemma B2, i=1: P S_i^-T - S_i(1/t) P = Matrix([[0, 0], [0, 0]])
Lemma B2, i=2: P S_i^-T - S_i(1/t) P = Matrix([[0, 0], [0, 0]])
NEG wrong P gives zero? False
B1 r12: Matrix([[0, 0, 0]])
B1 r23: Matrix([[0, 0, 0]])
det of (u,v,f) map: t**2 + t + 1
r_t on (u,l): 0 0
det of (a,b)->(u,l): 1
