He cuts a piece forming a circular sector of 60 degrees and flips the piece upside down, with the icing on the bottom.
2
令人惊奇的是，对于任意大小的扇形，即使圆心角是一个无理数：经过有限步之后，所有的糖衣都会回到上面。
Amazingly, this works for any piece size, even if the cutting Angle is an irrational number: all the icing will be back on top after a finite number of steps.
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