By an analytic method, in this essay a vector invariant of a casual point to a tetrahedron on volume and deductions form vector invariant are given. 摘要利用解析法，给出空间任意一点与四面体体积有关的一个向量恒等式，并给出若干推论。
An analytic method of determining the basic dimensions of the oscillating disk cam mechanism under retangular coordinates is introduced. 介绍了直角坐标下摆动从动件盘形凸轮机构基本尺寸确定的解析法。
