考试
按四等水准测量规范施测一条从水准点A出发的闭合水准路线,经过待测点l、2、3,4,5,最点后回到点A.测得各测段高差分别为h1=-2.237m,h2=1.185m,h3=-0.564m,h4=2.143m,h5=1.235m,h6=-1.785m.那么高差闭合差为()。
S1={1,2,...,8,9},S2={2,4,6,8},S3={1,3,5,7,9},S4={3,4,5},S5={3,5},在条件X⊆S1且X⊄S3下,X与( )集合可能相等。