论文标题
垂直线与非垂直线的交集
Intersections of vertical lines with non-vertical lines
论文作者
论文摘要
我们对一个问题进行负回答：如果$ \ Mathcal f $是$ n \ geqslant 3 $非垂直，成对的非并行线的家族，而$ \ bigcap \ mathcal f = \ emptyset $，是否有垂直线$ l $ l $ l \ big cap \ big cap \ big cap \ nathcal $ n-1 $ n-2？
We answer negatively a question: if $\mathcal F$ is a family of $n\geqslant 3$ non-vertical, pairwise non-parallel lines on the plane and $\bigcap \mathcal F=\emptyset$, is there a vertical line $L$ such that $L\cap\bigcup \mathcal F$ has exactly $n-1$ or $n-2$ points?
