MathDB
number of regions formed by partition in a triangle

Source: ISI(BS) 2005 #10

June 23, 2012
combinatorics proposedcombinatorics

Problem Statement

Let ABCABC be a triangle. Take nn point lying on the side ABAB (different from AA and BB) and connect all of them by straight lines to the vertex CC. Similarly, take nn points on the side ACAC and connect them to BB. Into how many regions is the triangle ABCABC partitioned by these lines?
Further, take nn points on the side BCBC also and join them with AA. Assume that no three straight lines meet at a point other than A,BA,B and CC. Into how many regions is the triangle ABCABC partitioned now?