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Learn about tangents, their properties, and how to solve problems involving circumscribed polygons. Explore the concept of a point of tangency and its significance. This lesson is part of Chapter 10-5 and aligns with Standard 7.0 and Standard 21.0.
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Chapter 10-5 Tangents
Use properties of tangents. • tangent • Solve problems involving circumscribed polygons. • point of tangency Standard 7.0Students prove and use theorems involving the properties of parallel lines cut by a transversal, the properties of quadrilaterals, and the properties of circles. (Key) Standard 21.0Students prove and solve problems regarding relationships among chords, secants, tangents,inscribed angles, and inscribed and circumscribed polygons of circles. (Key) Lesson 5 MI/Vocab
Reminder • Tangent—a line that intersects the circle in only one point
Secant Tangent Diameter Radius Point of Tangency Chord
Tangent Theorem • A line is tangent to a circle it is to a radius at its endpoint on the circle
Find Lengths Because y is the length of the diameter, ignore the negative result. Thus, y is twice QR or y = 2(12) = 24. Lesson 5 Ex1
A • B • C • D A. 15 B. 20 C. 10 D. 5 Lesson 5 CYP1
Identify Tangents Because the converse of the Pythagorean Theorem did not prove true in this case, ΔABC is not a right triangle. Lesson 5 Ex2
Identify Tangents First determine whether ΔEWDis a right triangle by using the converse of the Pythagorean Theorem. Because the converse of the Pythagorean Theorem is true, ΔEWD is a right triangle and EWD is a right angle. Lesson 5 Ex2
A • B • C A. yes B. no C. cannot be determined Lesson 5 CYP2
A • B • C A. yes B. no C. cannot be determined Lesson 5 CYP2
12 r 10 r r2 + 122 = (r + 10)2 r2 + 144 = r2 + 20r + 100 144 = 20r + 100 44 = 20r r =
C AC = AB A B • If two segments from the same external point are tangent to a circle they are
Congruent Tangents ALGEBRA Find x.Assume that segments that appear tangent to circles are tangent. Lesson 5 Ex3
10 10 Congruent Tangents Use the value of y to find x. Answer: 1 Lesson 5 Ex3
ALGEBRA Find a.Assume that segments that appear tangent to circles are tangent. • A • B • C • D A. 6 B. 4 C. 30 D. –6 Lesson 5 CYP3
Triangles Circumscribed About a Circle Interactive Lab: Tangents and Communication Signals 16 45 16 + 29 = 45 18 P = 16 + 18 + 18 + 45 + 45 + 16 = 158 Lesson 5 Ex4
A • B • C • D A. 86 B. 180 C. 172 D. 162 Lesson 5 CYP4
Common External Tangent Common Internal Tangent
Homework Ch 10-5 • Pg 593 5 – 22, 30, 31, 43 – 46