reserve w, w1, w2 for Element of ExtREAL;
reserve c, c1, c2 for Complex;
reserve A, B, C, D for complex-membered set;
reserve F, G, H, I for ext-real-membered set;
reserve a, b, s, t, z for Complex;
reserve f, g, h, i, j for ExtReal;
reserve r for Real;
reserve e for set;

theorem
  F /// (G \/ H) = (F///G) \/ (F///H)
proof
  thus F /// (G \/ H) = F**((G"")\/(H"")) by Th23
    .= (F///G) \/ (F///H) by Th82;
end;
