Hopf problem: period family · core 8

Supporting definitions and proofs for this stage of the six-sphere construction.

theorem Mathoverflow1973.PeriodFamily.GammaZero.triangleRealEquiv_gamma (g : SpecialPeriods.TriangleGroup) (x : RealPlane₄) : (SpecialPeriods.triangleRealEquiv g) x 0 = x 0