If an triangle ABC, A≡(1,10),circumcentre ≡(−1/3,  2/3), and orthocentre ≡(−11/3,  4/3), then the coordinates of the midpoint of the side opposite to A are

Circumcentre O≡(−1/3,2/3) and orthocenter H≡(11/3,4/3) Therefore, the coordinates of G are (1,8/9). Now, the point A is (1,10) as G is (1/ 8/9).Also, AD : DG =3:1∴    D≡(3−13−1,8/3−103−1)≡(1,11/3)∴    D=(3−12)=1, Dy=(8/3)−102=−113Hence, the coordinates of t'he midpoint of BC are (1,-11 /3).