∫01 | sin 2 π x | dx=
2π
π2
π
∫01|Sin2πx|dx=∫01/2|Sin2πx|dx+∫1/21|Sin2πx|dx
=∫01/2Sin2πx dx+∫1/21−Sin2πxdx
=(−Cos 2π x2π)012+(Cos 2π x2π)121
=42π=2π