Geometry: Common Core (15th Edition)

Published by Prentice Hall
ISBN 10: 0133281159
ISBN 13: 978-0-13328-115-6

Chapter 4 - Congruent Triangles - 4-5 Isosceles and Equilateral Triangles - Practice and Problem-Solving Exercises - Page 256: 30

Answer

𝑚 = 20 degrees 𝑛 = 45 degrees

Work Step by Step

2 sides of the INNER isosceles triangle are equal - given If both sides are equal, then both base angles are equal - Theorem 4-3 Isosceles Triangle Theorem Vertex of INNER isosceles triangle = 90 degrees - given 90 + 𝑛 + 𝑛 = 180 2𝑛 = 90 𝑛 = 45 degrees 2 sides of the OUTER isosceles triangle are equal - given If both side are equal, then both base angles are equal - Theorem 4-3 Isosceles Triangle Theorem Base angle = (𝑚 + 𝑛) - given 𝑛 = 45 - worked out above 50 + (𝑚 + 𝑛) + (𝑚 + 𝑛) = 180 50 + (𝑚 + 45) + (𝑚 + 45) = 180 (𝑚 + 45) + (𝑚 + 45) = 180 - 50 2(𝑚 + 45) = 130 (𝑚 + 45) = 65 𝑚 = 20 degrees
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