We are often tempted to quantify core-body rotation numerically - e. g. more than 30 but less than 90 degrees - but few of us are likely to carry a protractor to the pool to pin down the number.
我们经常尝试给转动定义个数据，比如大于30度小于90度。但是没有人会真的拿量角器到游泳池去量。
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Introduction: This useful toolbox contains 12 tools: Ruler, Angle Protractor, Exchange Rate, Stopwatch, Level, Plumb, Unit Converter, Light, My Position, Clothing Size, Body Mass Index, and Shoe Size.