reserve z,z1,z2 for Complex;
reserve r,x1,x2 for Real;
reserve p0,p,p1,p2,p3,q for Point of TOP-REAL 2;

theorem
  cpx2euc(z1-z2)=cpx2euc(z1)-cpx2euc(z2)
proof
  thus cpx2euc(z1-z2)=cpx2euc(z1+-z2) .=cpx2euc(z1)+cpx2euc(-z2) by Th7
    .=cpx2euc(z1)-cpx2euc(z2) by Th11;
end;
