... are satisfied:d1 θ dx, y for all x, y ∈ X and dx, yθ if and only if x y;d2 dx, ydy, x for all x, y ∈ X;d3 dx, y Kdx, zdz, y for all x, y, z ∈ X.The pair X, ... such thatdxn,x c for all n>n0. We write limn →∞xn x,orxn→ x, n →∞.c2 If for every c ∈ E with θ c there exists n0∈ such that dxn,xm c for alln, m > n0,then{xn} ... is satisfied in this case, too.Therefore, 3.3 is satisfied for all n ∈0, and by iterating we getdzn,zn1 αndz0,z1. 3.8Since K ≥ 1, for m>nwe havedzn,zm...