5

Part of 2001 APMO

Problems(1)

Find n if triangles are equal

Source: APMO 2001

Find the greatest integer

n

, such that there are

n+4

A

B

C

D

X_1,\dots,~X_n

in the plane with

AB\ne CD

that satisfy the following condition: for each

i=1,2,\dots,n

ABX_i

CDX_i

geometry unsolvedgeometry