MathDB

Problem 3 of Fourth round

Source: I International Festival of Young Mathematicians Sozopol 2010, Theme for 10-12 grade

December 15, 2019

geometrysymmetry

Problem Statement

Through vertex

C

\Delta ABC

are constructed lines

l_1

and

l_2

which are symmetrical about the angle bisector

CL_c

. Prove that the projections of

A

and

B

on lines

l_1

and

l_2

lie on one circle.