You find the Centroid of a triangle by graphing like this: To find the Centroid of a triangle, use the given formula from the following section that locates a point two-thirds of the distance from the vertex to the midpoint of the opposite side.
For example, to find the Centroid of a triangle with vertices at (0,0), (12,0) and (3,9), first find the midpoint of one of the sides.