図で理解したいのなら

Do[
Plot[
Sin[2 n x] Cos[x], {x, 0, Pi/2}, FrameLabel -> {x, Sin[
2 n x]Cos[x], None, None},
Frame -> True,
FormatType -> TraditionalForm,
TextStyle -> {FontSize -> 12},
PlotRange -> {{0, Pi/2}, {-1, 1}},
FrameTicks -> {{{0, 0}, {Pi/2, Pi/2}}, Automatic}
],
{n, 1, 100, 5}
]