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5.3: Concurrent Lines, Medians and Altitudes. Objectives: To identify properties of perpendicular bisectors and angle bisectors To identify properties of medians and altitudes of triangles. Vocabulary. Concurrent: 3 or more lines intersect at a point Point of Concurrency:
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5.3: Concurrent Lines, Medians and Altitudes Objectives: To identify properties of perpendicular bisectors and angle bisectors To identify properties of medians and altitudes of triangles
Vocabulary Concurrent: 3 or more lines intersect at a point Point of Concurrency: where the lines intersect
Circumcenter: The point of concurrency of the perpendicular bisectors of a triangle • If you were to draw a circle around a triangle, where each vertex of the triangle are points on the circle, the circle would be circumscribed about that triangle • The circumcenter of the triangle is ALSO the center of the circle circumscribed about it
Perpendicular bisectors of the sides of a triangle are concurrent at a point equidistant from the vertices of the triangle
Perpendicular Bisectors Acute triangle: Circumcenter inside triangle Right triangle: Circumcenter lies ON the triangle Obtuse Triangle: Circumcenter is outside triangle
Find the center of the circle that you can circumscribe about the triangle with vertices (0, 0), (-8,0) and (0,6). • Plot the points on a coordinate plane. • Draw the triangle • Draw the perpendicular bisectors of at least 2 sides. • The circumcenter of this triangle will be the center of the circle.
Incenter of a triangle: point of concurrency of the angle bisectors A circle is inscribed in a triangle when the circle is tangent to each side (also called an incircle) The incenter of a triangle is the center of an inscribed circle
ANGLE BISECTORS of a triangle are concurrent at a point equidistant to the sides of the triangle. (The incenter is equidistant to the sides) • The incenter of ALL types of triangles is always INSIDE the triangle.
Median of a Triangle A segment whose endpoints are a vertex of a triangle and the midpoint of the opposite side
WHAT IS THE DIFFERENCE BETWEEN A MEDIAN AND A PERPENDICULAR BISECTOR??
CENTROID: Point of concurrency of medians of a triangle The medians of a triangle intersect at a point that is 2/3 the distance from the vertex to the midpoint of the opposite side. G is the centroid AG = AD BG = BF CG= CE
O is the centroid of triangle ABC. CE = 11 FO = 10 CO = 8 Find EB. Find OD. Find FB. Find CD. If AO = 6, find OE.
Altitude of a Triangle The perpendicular segment from the vertex to the line containing the opposite side Obtuse Triangle: Outside Acute Triangle: Inside Right Triangle: Side
What is the difference between an altitude and a perpendicular bisector?
Orthocenter of a Triangle Point of concurrency for altitudes of a triangle Acute Triangle: Inside Right Triangle: Vertex Obtuse Triangle: Outside