MathDB
Concurrency

Source: Iran TST 2008

May 20, 2008
geometryincenterprojective geometrygeometry proposed

Problem Statement

Suppose that I I is incenter of triangle ABC ABC and l′ l' is a line tangent to the incircle. Let l l be another line such that intersects AB,AC,BC AB,AC,BC respectively at C′,B′,A′ C',B',A'. We draw a tangent from A′ A' to the incircle other than BC BC, and this line intersects with l′ l' at A1 A_1. B1,C1 B_1,C_1 are similarly defined. Prove that AA1,BB1,CC1 AA_1,BB_1,CC_1 are concurrent.
Back to ProblemsView on AoPS