This third triangle results by first finding the orthocenter of an arbitrary triangle. Recall that the orthocenter is the point where the three altitudes of the original triangle are concurrent. Next, we need to draw segments from each vertex to the orthocenter. Then, we need to find the midpoints of each of those segments. Finally, our triangle is generated by connecting those midpoints. Let's see how that might look for any arbitrary triangle:

Here, we can clearly see the triangle generated by connecting the midpoints of the segments from the orthocenter to each vertex, respectively. This triangle is shown in green, and the orthocenter is represented by the point H.