HMMT 二月 2000 · POW 赛 · 第 19 题
HMMT February 2000 — POW Round — Problem 19
题目详情
- Supp ose w e ha v e n lines in a plane in general p osition, whi h means that none are parallel to ea h other and that no three of these lines in terse t at a single p oin t. Find the n um b er of regions that these lines divide the plane in to... (a) in a re ursiv e form. (b) in a nonre ursiv e form ula.
解析
- (a) r = r + n n n 1 n +1 (b) + 1 2