由向量基本定理可知,只要选择不共面的一组向量a,b,c作基底,则任意向量p即可由a,b,c线性表示.即p可以分解为a,b,c的线性组合写成p=xa+yb+zc的形式,这里x,y,z被a,b,c唯一确定.空间四边形的任意三边是不共面的,因此可以用任意三边所在的向量作为空间的一组基底,那么第四条边即可表示出来.于是,运用向量的有关知识可以推导出空间四边形的一些结论. From the vector theorem, we can see that if we choose a set of vectors a, b, and c that are not coplanar as the basis, the arbitrary vector p can be expressed linearly by a, b, and c. That is, p can be decomposed into a linear combination of a, b, and c. Write the form of p=xa+yb+zc, where x,y,z are uniquely determined by a,b,c. Any three sides of the space quadrilateral are not coplanar, so you can use any three sides of the vector as spatial A set of bases, then the fourth edge can be represented. Therefore, using the knowledge of the vector can derive some conclusions of the space quadrilateral.