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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. Exploring Perpendicular Bisectors in a triangle.
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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
Exploring Perpendicular Bisectors in a triangle • Concurrent – 3 or more lines intersect at one point: thepoint of concurrency. 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?
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 ∆
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
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
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
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.
A) GE = 2x – 7; GF = x + 4 What is GD? B) QN = 5x + 36; QM = 2x + 51 What is QO? EX 3: Calculate the length of the segment.
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?
5-2 Classwork • Core book pgs 201 – 202 #1 – 3, 7 – 9 • Textbook pg 323 – 324 #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