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Congruent Triangles 4.52 Importance of concurrency

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**Triangle Points of Concurrency**

#1 Perpendicular bisectors and the circumcenter.

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Circumcenter Before we can talk about the circumcenter’s importance, we need some review on perpendicular bisectors.

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**perpendicular bisector is equidistant from A and B.**

Review of Perpendicular Bisector Properties. Every point on the perpendicular bisector is equidistant from A and B.

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**Therefore, the circumcenter is equidistant from**

each vertex. Why ?

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**Since C is on each perpendicular bisector it is equidistant from each segment’s endpoint.**

Therefore…

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**Ergo the term… Circumcenter.**

The equal distances are radii for a circle that is … written around (circumscribed) the circle. Ergo the term… Circumcenter.

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Why is this important? If A, B, and T are three cities, Point C is the ideal place to build a communication tower to broadcast to each city.

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**Triangle Points of Concurrency**

#2 Angle bisectors and the Incenter.

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**From any general point on the angle bisector, the perpendicular distance to either side is the same.**

Why ? Y X P

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**The top angles are congruent by definition of angle bisector.**

There are two right angles are congruent by def. of perpendicular. Y by the reflexive property of = X ? By AAS P ? By CPCTC

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**Let’s see. Why is this important ? Each new point creates**

2 congruent triangles by AAS. Why is this important ? Let’s see.

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**Since the incenter P is on each angle bisector….**

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**P Why is this important? Point P is equidistant from each side.**

Remember, the distance from a point to a line is the brown perpendicular segment. P Why is this important? Because these equal distances are radial distances.

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**Radial distances refer to a circle.**

The incenter generates an inscribed circle. P

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**Triangle Points of Concurrency**

#3 Medians and the Centroid.

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**A median is a segment connecting the vertex to the midpoint of a side of a triangle.**

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**The 3 medians meet at the centroid – point P.**

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**Each little triangle is unique, yet they all have something in common.**

What is it ?

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**the triangle will balance on the centroid.**

Since the areas of the little triangles around the centroid E are the same, … the triangle will balance on the centroid.

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**Calder’s Mobile at the East Wing of the National Gallery of Art**

Mobiles balance objects in an artistic form. Calder’s Mobile at the East Wing of the National Gallery of Art In Washington DC.

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**Triangles balanced at their centroids.**

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**The birds are tied to their centers of balance**

or centroids.

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**Triangle Points of Concurrency**

#4 Altitudes and the Orthocenter.

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Acute Triangle The point of concurrency is called… The Orthocenter

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Right Triangle The point of concurrency is called… The Orthocenter

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Obtuse Triangle Notice that although the altitudes are not concurrent…

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**Obtuse Triangle The Orthocenter**

The lines containing the altitudes are concurrent.

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**So what do you think is the importance or practical application of the orthocenter is?**

Nothing !!! It is just an interesting fact that mathematicians have discovered. Psych Isn’t this FUN !!!

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**Summary None Medians Orthocenter Altitudes Circumcenter Incenter**

Line Type Concurrency Point Importance Equidistant from the vertices Circumcenter Circumscribed Circle Equidistant from the sides Incenter Inscribed Circle Medians Centroid Center of Balance None Altitudes Orthocenter

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**C’est fini. Good day and good luck. A Senior Citizen Production**

That’s all folks. A Senior Citizen Production

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Medians, and Altitudes. When three or more lines intersect in one point, they are concurrent. The point at which they intersect is the point of concurrency.

Medians, and Altitudes. When three or more lines intersect in one point, they are concurrent. The point at which they intersect is the point of concurrency.

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