MathDB

Prove they are on aline [about mixtilinear incircles]

Source: Iran 2002 3rd round

April 9, 2004

geometryincentercircumcirclegeometric transformationhomothetyratiotrapezoid

Problem Statement

A,B,C

are on circle

\mathcal C

I

is incenter of

ABC

D

is midpoint of arc

BAC

W

is a circle that is tangent to

AB

and

AC

and tangent to

\mathcal C

P

. (

W

is in

\mathcal C

) Prove that

P

and

I

and

D

are on a line.