1. Chapter 5 Lesson 3
Objective: To identify properties of medians and altitudes of a triangle.

2. A median of a triangle is a segment whose endpoints are a vertex and the midpoint of the opposite side.

3. Theorem 5-8
The medians of a triangle are concurrent at a point that is two thirds the distance from each vertex to the midpoint of the opposite side.

4. In a triangle, the point of concurrency of the medians is the centroid.
The point is also called the center of gravity of a triangle because it is the point where a triangular shape will balance.

5. Example 1: Finding Lengths of Medians
D is the centroid of ∆ABC and DE = 6. Find BE.
Since D is a centroid, BD =  BE and DE = BE.
                                                                                                    

6. Example 2: Finding Lengths of Medians
Use Example 1 to find BD.
BD =  BE

7. An altitude of a triangle is the perpendicular segment from a vertex to the line containing the opposite side. Unlike angle bisectors and medians, an altitude of a triangle can be a side of a triangle or it may lie outside the triangle.

8. Example 3: Identifying Medians and Altitudes
Is ST a median, an altitude, or neither? Explain.
ST is an altitude; perpendicular segment from a vertex

9. Example 4: Identifying Medians and Altitudes
Is UW a median, an altitude, or neither? Explain.
Median; UW is a segment drawn from vertex U to the midpoint of the opposite side.

10. The lines that contain the altitudes of a triangle are concurrent.
The lines containing the altitudes of a triangle are concurrent at the orthocenter of a triangle.
Theorem 5-9  
The lines that contain the altitudes of a triangle are concurrent.

11. Assignment:
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