plane curve短语⁴⁷¹¹² 基本例句 平面曲线 This paper has proved that a plane curve cis a circle if and only ifc is the locus of a moving point that has a constant second power average of distances from n fixed points. 本文提出了确定内燃机配气机构刚度的三种数据处理方法，并对处理结果作出了分析、比较，确认二次刚度平均法是一种较好的实用方法。 dictall