How to define a median in a triangle.
How to relate corresponding altitudes, medians and angle bisectors in similar triangles.
How to define a midsegment in a triangle.
How to identify the centroid and the way it divides each of the medians.
How to identify a segment from the vertex angle in an isosceles triangle to the opposite side.
How to define point of concurrency; how to identify the four main points of concurrency in triangles.