| Abstract: | The circumcentre E of a triangle ABC is defined, as in figure 1, by the two relations EA = EB EB = EC The other centres (such as the incentre, the centroid, etc.) can be defined by two similar relations. This note is an elaboration on the simple fact that if two centres of a triangle coincide then it is equilateral. We take a certain centre of a given triangle and investigate what can be deduced from the assumption that it satisfies one of the two defining relations of another centre. This is done for each pair of, what one may think of as, the seven most natural centres. |
