Hello everyone,

I am learning the Wolfram Mathematica language doing some simple programs but i got stuck. I was writing code that show a parametric curve and its derivate, with a tangent vector for each one and the module of vector velocity. The problem is that when i enable dynamic updating the yellow dot on the icon of Wolfram in the application bar starts blinking red and the module of the vector change even if the vector is still. It's the first time i get this errors, and i don't know why. If someone could help me, i left the code here, i hope it's well written. Thank you.

     Module[
 {f, g},

 Manipulate[

  f[x_] := x Cos[x];
  g[x_] := x Sin[x];

  plot1 = Graphics[
    {
     {Blue, Arrow[{{0, 0}, {f[n], g[n]}}]},
     {Orange, Arrow[{{0, 0}, {f'[n], g'[n]}}]},
     {Red, Arrow[{{f[n], g[n]}, {f'[n] + f[n], g[n] + g'[n]}}]},
     {Purple, Arrow[{{f'[n], g'[n]}, {f'[n] + f''[n], g'[n] + g''[n]}}]}
     }];

  plot2 = ParametricPlot[
    {
     {f[x], g[x]},
     {f'[x], g'[x]}
     },
    {x, 0, 2 Pi}
    ]; 

  Show[{
    plot1,
    plot2
    },
   Axes -> {True, True}, PlotRange -> {{-5, 9}, {-7, 9}}
   ],
  {n, 0, 2 Pi}, Delimiter,
  Dynamic@
   Style["T =" <>  ToString[NumberForm[N[Sqrt[(f'[x])^2 + (g'[x])^2]], 3]], 
    FontFamily -> "Arial", FontSize -> Medium, FontColor -> Col]
  ]
 ]