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GEOMETRY Medians and altitudes of a Triangle. Median of a triangle A median of a triangle is a segment from a vertex to the midpoint of the opposite side.

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Presentation on theme: "GEOMETRY Medians and altitudes of a Triangle. Median of a triangle A median of a triangle is a segment from a vertex to the midpoint of the opposite side."— Presentation transcript:

1 GEOMETRY Medians and altitudes of a Triangle

2 Median of a triangle A median of a triangle is a segment from a vertex to the midpoint of the opposite side. median

3 Centroid of a triangle The medians of a triangle intersect at the centroid, a point that is two thirds of the distance from each vertex to the midpoint of the opposite side. The centroid of a triangle can be used as its balancing point. A B C D E F P This is also a 2:1 ratio

4 Solving problems from involving medians and centroids If you know the length of the median P is the centroid, find BP and PE, given BE = 48 AB C D E F P 2 : 1 so BP=32 PE=16

5 Solving problems from involving medians and centroids If you know the length of the segment from the vertex to the centroid P is the centroid, find AD and PD given AP = 6 AB C D E F P

6 Solving problems from involving medians and centroids If you know the length of the segment from the midpoint to the centroid P is the centroid, find AD and AP given PD = 9 AB C D E F P

7 Find the Centroid on a Coordinate Plane SCULPTURE An artist is designing a sculpture that balances a triangle on top of a pole. In the artists design on the coordinate plane, the vertices are located at (1, 4), (3, 0), and (3, 8). What are the coordinates of the point where the artist should place the pole under the triangle so that it will balance? You need to find the centroid of the triangle. This is the point at which the triangle will balance.

8 Find the Centroid on a Coordinate Plane

9 Your Turn BASEBALL A fan of a local baseball team is designing a triangular sign for the upcoming game. In his design on the coordinate plane, the vertices are located at (–3, 2), (–1, –2), and (–1, 6). What are the coordinates of the point where the fan should place the pole under the triangle so that it will balance?

10 An altitude of a triangle is a perpendicular segment from a vertex to the line containing the opposite side. Every triangle has three altitudes. An altitude can be inside, outside, or on the triangle. altitude of a triangle

11 Altitude of an Acute Triangle Point of concurrency P or orthocenter The point of concurrency called the orthocenter lies inside the triangle.

12 Altitude of a Right Triangle Point of concurrency P or orthocenter The point of concurrency called the orthocenter lies on the triangle. The two legs are the altitudes

13 Altitude of an Obtuse Triangle The point of concurrency of the three altitudes is called the orthocenter altitude The point of concurrency lies outside the triangle.

14 In ΔQRS, altitude QY is inside the triangle, but RX and SZ are not. Notice that the lines containing the altitudes are concurrent at P. This point of concurrency is the orthocenter of the triangle. orthocenter of the triangle

15 Special Segments in Triangles NameType Point of Concurrency Center Special Quality From / To MediansegmentCentroid Center of Gravity Vertex midpoint of segment AltitudesegmentOrthocenternoneVertex none

16 ALGEBRA Points U, V, and W are the midpoints of respectively. Find a, b, and c. try it


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