2. The medians of a triangle intersect in the centroid, labeled here by S. S divides each median in the ratio 2 : 1 (from the vertex!)
3. According to the text the median and are perpendicular. That means you have 2 right triangles.
4. Use Pythagorean theorem and you'll get a system of equations:
Solve for m and s.
5. Use Pythagorean theorem to calculate the length of the side :
You should come out with