Plotting Derivatives

f[x_]=Cos[x]; g[x_]=Sqrt[x]*Sin[x]; h[x_]=Cos[Sqrt[x]*Sin[x]];
Plot[{f[x],f'[x],g[x],g'[x],h[x],h'[x]},{x,0,15},
         PlotStyle->{RGBColor["#3636FF"],Darker[Blue],RGBColor["#FF3636"],
         Darker[Red],RGBColor["#FF36FF"],Darker[Magenta]},
         Filling->Axis,FillingStyle->Opacity[0.2],ImageSize->Large,
         GridLines->Automatic,PlotLegends->"Expressions"]