1.同九年级第1题.2.圆周上给定的n个点A_i(1≤i≤n)将圆周分成n段圆弧(称为旧弧).现将圆周绕圆心旋转(?)(k∈N+),点A_i转到B_i-B_i也将圆周分成n段圆弧(称为新弧).证明:存在一段新弧含在某段旧弧中(圆弧的端点约定属于该圆弧).3.求出所有的正整数k,使得前k个素数的乘积减去1是一个正整数的大于1的整数 1. Same as grade 9 of grade 1. 2. The n points given on the circumference A_i (1≤i≤n) divide the circle into n arcs (called old arcs). Now rotate the circle around the center of the circle (?) (k ∈ N +) and point A_i to B_i-B_i also divides the circle into n arcs (called new arcs). Proof: A new arc exists in some old arc (the end point of the arc belongs to the circle Arc) .3. Find all positive integers k such that the product of the first k primes minus 1 is a positive integer greater than 1