第一天1.如图1,两圆Γ1、Γ2交于点A、B,过点B的一条直线分别交圆Γ1、Γ2于点C、D,过点B的另一条直线分别交圆Γ1、Γ2于图1点E、F,直线CF分别交圆Γ1、Γ2于点P、Q.设M、N分别是弧PB、QB的中点.若CD=EF,求证:C、F、M、N四点共圆.(熊斌供题)2.设整数k≥3,数列{an}满足ak=2k,且 Day 1 1. As shown in Figure 1, two circles Γ1 and Γ2 are intersected with points A and B, and a straight line passing through point B intersects Γ1 and Γ2 separately from point C and D and the other straight line passing through point B intersects Γ1 , Γ2 in Figure 1 point E, F, respectively, the intersection of straight line CF Γ1, Γ2 at the point P, Q. Let M, N are the midpoints of the arc PB, QB. , N four-point total circle. (Xiong Bin for the title) 2 set the integer k ≥ 3, the sequence {an} satisfy ak = 2k, and