4-18
Prove that for any triangle , H, G, C are collinear, and prove that HG= 2GC
Given any triangle, we can construct G, O, and H.
Centroid (G) : the intersection of the three medians.
Circumcenter (O) : This point is equidistance from the three vertics ,which formed by perpendicular bisectors of each side of triangle.
Orthocenter(H) : the intersection of the three altitudes of each side of triangle.