If a circle passes through the feet of perpendicular (D,E,F) mid points of sides BC, CA, AB sespectivcly (H,I,J) and mid points of the line joining the orthocentre O to the angular points A,B,C (K,L,M) thus the nine points D,E,F H,I,J, K,L,M all lie on a circle, This circle is known as nine point circle and its centre is called nine point centre.
1. The orthocentre (O), nine point centre (N) centroid (G) and circumcentre (C) all lie in the same line i.e. ONGC (oil natural gas corporation)
2. The nine point centre bisects the join of orthocentre (O) and circumcentre (C)
3. The radius of nine point circle is half the radius of circumcircle.
