第一天1.如图1,O是△ABC的外心,点D、E、F分别在线段BC、CA、AB上,使得DE⊥CO,DF⊥BO.设K为△AFE的外心,证明:DK⊥BC.2.设n是一个给定的正整数.求最大的正整数m,使得具有如下性质:存在一张m行n列的实数数表,满足对任意两行数[a_1,a_2,…,a_n]和[b_1,b_2,…,b_n]均有 First Day 1. As shown in Figure 1, O is the outer center of △ ABC, and points D, E, F are on the segments BC, CA, AB, respectively, so that DE⊥CO, DF⊥BO. , Prove: DK ⊥ BC.2. Let n be a given positive integer. Find the largest positive integer m such that it has the following properties: There is a real number table of m rows and n columns, satisfying any two rows [ a_1, a_2, ..., a_n] and [b_1, b_2, ..., b_n]