Triangle ABC is given with its centroid G and cicumcentre O is such that GO is perpendicular to AG. Let A′ be the second intersection of AG with circumcircle of triangle ABC. Let D be the intersection of lines CA′ and AB and E the intersection of lines BA′ and AC. Prove that the circumcentre of triangle ADE is on the circumcircle of triangle ABC. geometrycircumcircleratiogeometric transformationhomothetygeometry unsolved