MathDB
DE _|_AC if DF _|_ AB

Source: 2021 IMOC qualification problem, G2

December 30, 2021
geometryperpendicular

Problem Statement

Given a triangle ABCABC, DD is the reflection from the perpendicular foot from AA to BCBC through the midpoint of BCBC. EE is the reflection from the perpendicular foot from BB to CACA through the midpoint of CACA. FF is the reflection from the perpendicular foot from CC to ABAB through the midpoint of ABAB. Prove: DE⊥ACDE \perp AC if and only if DF⊥ABDF \perp AB
Back to ProblemsView on AoPS