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 Th21:
  |.euc2cpx(p).|=sqrt ((p`1)^2+(p`2)^2)
proof
  Re euc2cpx(p)=p`1 by COMPLEX1:12;
  hence thesis by COMPLEX1:12;
end;
