本文指出了周衍柏编《理论力学教程》第二版中计算力学体系约束力的两处公式的推证错误；
In this paper two erroneous formulas, which discuss constraint forces of mechanical system in Theoretical Mechanics second edition write by Zhou Yengbor, have been indicated and analyzed.
通过对周衍柏编写的《理论力学教程》第二版中的弧坐标中质点加速度表达式的推导作些改进。
In the book Course of Theorical Mechanics by Yanbai Zhou there are some mistakes about the expression of acceleration in arc coordinates, this paper has corrected them.
该动作衍发于团身后空翻三周，但其动作技术和素质及专项能力要求都要高于后者。
Movement this is it take place on is it backward roll ong week to bunch up that but its movement tecnology and quality and special ability demand to be higher than the latter.
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