The Midpoint Theorem states that the segment joining two sides of a triangle at the midpoints of those sides is parallel to the third side and is half the length of the third side. We can use this information to find the lengths of the sides of the triangle. The mid-point of the line segment is the geometric centre of the line segment. Mid-point of a line segment divides it into two halves. Midpoint theorem plays a vital role in mathematics. Given a triangle, if we connect two sides with a line segment, and this line segment joins each of the two sides at the centres, or midpoints of each side, we can know two fundamental aspects about the triangle and the relationships between the sides. We shall see this in mid-point theorem and converse of midpoint theorem. The line segment joining the midpoints of two sides of a triangle is parallel to the third side and half its length. If D and E are the midpoints of AC and BC, respectively, then.