1. 5-2 Bisectors of a Triangle
Rigor: apply the perpendicular bisector theorem, the angle bisector theorem, and their converses
Relevance: City planning and interior design

2. Exploring Perpendicular Bisectors in a triangle
Draw a triangle (any triangle) on a piece of tracing paper
Fold each side in half. The creases are the perpendicular bisectors of each side.
What do you notice?
Concurrent – 3 or more lines intersect at one point: the point of concurrency.

3. Circumcenter – the point of concurrency of the ┴ bisectors
Concurrency of Perpendicular Bisectors Theorem – the circumcenter of a ∆ is
equidistant from the vertices
AP = BP = CP
Circumcenter can be inside, outside, or on ∆

4. Circumscribed Circles
Circumscribed circle – a circle that has all 3 vertices of a triangle on the circle with the center of circle as the circumcenter of the triangle
The prefix circum- means “around”, so a circumscribed circle goes around the triangle
Turn in your core book to page 199 EX 1 and construct a circumscribed circle

5. EX 1: What are the coordinates of the circumcenter of ∆ with vertices A(2,7), B(10,7) & C(10,3)
Step 1: Graph ∆
Step 2: Calculate midpoints (count if vertical or horizontal sides)
Step 3: Use right angle to draw ┴ bisector

6. EX 2: City Planning

7. Angle Bisectors and Incenters
Inscribed circle – a circle that touches every side of the triangle with the incenter as its center
Turn to pg 200 in the core book and construct an inscribed circle

8. Concurrency of Angle Bisectors Theorem
Incenter – the point of concurrency of the angle bisectors; always inside the triangle
Theorem: The incenter of a triangle is equidistant from the sides to the triangle.

9. EX 3: Calculate the length of the segment.
A) GE = 2x – 7;
GF = x + 4
What is GD?
B) QN = 5x + 36;
QM = 2x + 51
What is QO?

10. EX 4: Camping
Logan plans to go camping in a state park. The park is bordered by 3 highways, and Logan wants to pitch his tent as far away from the highways as possible. Should he set up camp at the circumcenter or the incenter of the park? Why?

11. 5-2 Classwork Core book pgs 201 – 202 #1 – 3, 7 – 9
Textbook pg 323 – #9, 10, 14 – 16, 20, 22, 23, 26 – 32
5-2 Homework
Core book pg 203 – 204 ALL
Due Thursday for periods 1, 3, 5
Due Friday for periods 2, 4, 7