reserve r, r1, r2, x, y, z,
        x1, x2, x3, y1, y2, y3 for Real;
reserve R, R1, R2, R3 for Element of 3-tuples_on REAL;
reserve p, q, p1, p2, p3, q1, q2 for Element of REAL 3;
reserve f1, f2, f3, g1, g2, g3, h1, h2, h3 for PartFunc of REAL,REAL;
reserve t, t0, t1, t2 for Real;

theorem
  for f being FinSequence of REAL st len f = 3 holds f is Element of REAL 3
proof
    let f be FinSequence of REAL;
    assume
A1: len f = 3;
    reconsider x1 = f.1, x2 = f.2, x3 = f.3 as Element of REAL
           by XREAL_0:def 1;
    <*x1,x2,x3*> is Element of 3-tuples_on REAL by FINSEQ_2:104;
    hence thesis by A1,FINSEQ_1:45;
end;
