> restart:
> ValNum:=x=1,y=1;
> f1:=sqrt(x^2+y^2);
> f2:=arctan(y/x);
> g11:=diff(f1,x);
> g21:=diff(f1,y);
> g12:=diff(f2,x);
> g22:=diff(f2,y);
> evalf(subs(ValNum,<f1|f2>));
> evalf(subs(ValNum,<<g11,g21>|<g12,g22>>));

                        ValNum := x = 1, y = 1


                                  2    2 1/2
                          f1 := (x  + y )


                          f2 := arctan(y/x)


                                     x
                         g11 := ------------
                                  2    2 1/2
                                (x  + y )


                                     y
                         g21 := ------------
                                  2    2 1/2
                                (x  + y )


                                       y
                        g12 := - -------------
                                    /      2 \
                                  2 |     y  |
                                 x  |1 + ----|
                                    |      2 |
                                    \     x  /


                                     1
                         g22 := ------------
                                  /      2 \
                                  |     y  |
                                x |1 + ----|
                                  |      2 |
                                  \     x  /


                     [1.414213562, 0.7853981634]


                   [0.7071067810    -0.5000000000]
                   [                             ]
                   [0.7071067810    0.5000000000 ]

> 
