reserve k,m,n for Element of NAT,
  i, j for Nat,
  a, b, c for object,
  X, Y, Z for set,
  D, D1, D2 for non empty set;
reserve p, q, r, s for FinSequence;
reserve t, u, v, w for GRZ-formula;
reserve R, R1, R2 for GRZ-rule;
reserve A, A1, A2 for non empty Subset of GRZ-formula-set;
reserve B, B1, B2 for Subset of GRZ-formula-set;
reserve P, P1, P2 for GRZ-formula-sequence;
reserve S, S1, S2 for GRZ-formula-finset;
reserve x, y, z for LD-EqClass;

theorem Th88:
  for x ex t st x = LD-EqClassOf t
proof
  let x;
  x in Class LD-EqR;
  then consider a such that
  A1: a in GRZ-formula-set and
  A2: x = Class(LD-EqR, a) by EQREL_1:def 3;
  reconsider t = a as GRZ-formula by A1;
  take t;
  thus thesis by A2;
end;
