proposition: Lemma distance_Tensor:forall a b c d e f g h r x y, e*y*r+f*y+g*r+h<>0 -> e*x*r+f*x+g*r+h<>0 -> ((a*y*r+b*y+c*r+d)/(e*y*r+f*y+g*r+h)) - ((a*x*r+b*x+c*r+d)/(e*x*r+f*x+g*r+h))= ((y-x)*((a*r+b)*(g*r+h)-(c*r+d)*(e*r+f)))/((e*y*r+f*y+g*r+h)*(e*x*r+f*x+g*r+h)).
proof: Proof. intros a b c d e f g h r x y Hcyd Hcxd; rewrite Rminus_Rdiv; auto; apply (f_equal2 Rdiv); ring. Qed.
imports: Reals QArithSternBrocot(R_addenda) Fourier