Plot[{x,}, {x, 0, 1}]

Show[%, %%]

tourner l' 
      angle pour matérialierle cos

Do[
Show[
ParametricPlot[{Sin[x], Cos[x]}, {x, 0, t}, AspectRatio -> 1, 
          PlotRange -> {{-1, 1}, {-1, 
                1}}, 
DisplayFunction -> 
            Identity], 
ParametricPlot[{Sin[x], x}, {x, 0, 
            t}, 
DisplayFunction -> Identity, 
          PlotStyle -> 
            RGBColor[1, 0, 
              0] ], 
DisplayFunction -> $DisplayFunction]
 
, {t, 0, 2 Pi/10 , 
        Pi/10}]

definit la fréquence

Plot[{Sin[2  x]}, {x, 0, 10 Pi}, 
      AspectRatio -> 1]

Play[{Sin[200   2  3.14 t ]}, {t, 
        0,  .1}]

Plot[{Sin[2  x]}, {x, 0, 10 Pi}, 
      AspectRatio -> 1]

famplitude modulée

Plot[{  Sin[ .2  x ] Sin[10 x] }, {x, 0, 
        10 Pi}, AspectRatio -> 1]

Plot[{  Sin[ x  + 0.2  Sin[2   x] ]}, {x, 0, 
        20 Pi}, AspectRatio -> 1]

3.  10^8 /10^9

3.  10^8 /10^9