Step 1: Given these three sides.

Step 2: Choose one side. Use the endpoints of this side as centers of circles with radius equal to the other two sides.

Step 3: Mark one of the points where these two circles intersect. Construct the segments from this point to the endpoints of the first line segment. You have constructed the triangle formed from the medians of another triangle. This is called the Medial triangle.

Step 4: Now construct parallel lines of each side of the triangle at the vertex opposite this side.

Step 5: Mark the points of intersection. Construct line segments at these three points.

Step 6: You now have constructed a triangle whose medians are the three line segments given above.