reserve x,y,y1,y2 for set,
  p for FinSequence,
  i,k,l,n for Nat,
  V for RealLinearSpace,
  u,v,v1,v2,v3,w for VECTOR of V,
  a,b for Real,
  F,G,H1,H2 for FinSequence of V,
  A,B for Subset of V,
  f for Function of the carrier of V, REAL;
reserve K,L,L1,L2,L3 for Linear_Combination of V;
reserve l,l1,l2 for Linear_Combination of A;

theorem Th27:
  f (#) <* v1,v2 *> = <* f.v1 * v1, f.v2 * v2 *>
proof
A1: len(f (#) <* v1,v2 *>) = len<* v1,v2 *> by Def7
    .= 2 by FINSEQ_1:44;
  then
A2: dom(f (#) <* v1,v2 *>) = {1,2} by FINSEQ_1:2,def 3;
  2 in {1,2} by TARSKI:def 2;
  then
A3: (f (#) <* v1,v2 *>).2 = f.(<* v1,v2 *>/.2) * <* v1,v2 *>/.2 by A2,Def7
    .= f.(<* v1,v2 *>/.2) * v2 by FINSEQ_4:17
    .= f.v2 * v2 by FINSEQ_4:17;
  1 in {1,2} by TARSKI:def 2;
  then (f (#) <* v1,v2 *>).1 = f.(<* v1,v2 *>/.1) * <* v1,v2 *>/.1 by A2,Def7
    .= f.(<* v1,v2 *>/.1) * v1 by FINSEQ_4:17
    .= f.v1 * v1 by FINSEQ_4:17;
  hence thesis by A1,A3,FINSEQ_1:44;
end;
