i dont get the bit where it refers to "1.1". not sure what theory they are referring to. i get the rest. i dont have access to the rest of the textbook

if theres a nice place where i can get access to proofs that H, G, O are in ratio of 2:1, and that they lie on the same straight line using BOTH euclidian geometry and vectors..that would be appreciated.

also , how do i show that H, G, O lie on the line, IN THAT PARTICULAR ORDER?

Thanks everybody

the circumcenter O, centroid G and orthocenter H