MathDB
Conditional geo with incenters

Source: Bulgaria MO Regional round 2024, 12.1

February 13, 2024
geometry

Problem Statement

Let ABCABC be an acute triangle with midpoint MM of ABAB. The point DD lies on the segment MBMB and I1,I2I_1, I_2 denote the incenters of ADC\triangle ADC and BDC\triangle BDC. Given that I1MI2=90\angle I_1MI_2=90^{\circ}, show that CA=CBCA=CB.