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MSM07G6_RESBK_Ch08_037-045.pe 2/6/06 4:09 PM Page 38 Name LESSON Date Class Practice B 8-5 Triangles Use the diagram to find the measure of each indicated angle. 1. !CBD 90° 2. !DAC 45° 3. !ABC 90° 4. !EBA 90° 5. !ACB 45° D E B 45° 45° C A Classify each triangle using the given information. 6. The perimeter of the triangle is 30 in. 10 in. 10 in. 7. The perimeter of the triangle is 15 cm. 8. The perimeter of the triangle is 22 ft. 8 ft 5 cm 3 cm euilateral scalene 6 ft isosceles 9. The angles of a triangular sail measure 90°, 30°, and 60°. Its sides measure approximately 2 feet, 3.5 feet, and 4 feet. Classify the triangular shape of the sail in two different ways. It isle. 10. Two angles in one triangle are congruent to two angles in another triangle. What can you conclude about the third angle in both triangles? ruent. Copyright © by Holt, Rinehart and Winston. All rights reserved. 38 Holt Mathematics MSM07G6_RESBK_Ch08_095-117.pe 2/7/06 9:36 AM Page 103 Puzzles, Twisters & Teasers 8-4 What is my Line? Reading Strategies 8-4 Understanding Symbols LESSON LESSON Use the figure on the right. For each box decide whether the statement is true or false. If it is false, black out the box. Parallel lines are the same distance apart and never meet. The lines on a ruled piece of paper are similar to parallel lines. The symbol || stands for parallel. A C E G I K Segment AB is parallel to segment CD. This can be written: AB || CD. B D F H J L "!# FG ! "!# HJ A "!# FG ! "!# GJ G "!# HJ " "!# FG C K F "!# FH " "!# GJ B "!# FH ! "!# HJ W "!# FH " "!# HJ L "!# FG " "!# FH R "!# HJ ! "!# GJ S "!# GJ " "!# KL D "!# AD ! "!# AG E "!# BC & "!# CD are skew P "!# DC " "!# EF G 1. Find another pair of parallel line segments in the figure above. Possible answer: ! GH and ! IJ G H J L 2. Use the || symbol to write how the line segments are related. ! GH || ! IJ Perpendicular lines meet to form square corners. T Square corner The symbol ! stands for perpendicular. A square corner is used as a symbol to indicate that two lines are perpendicular to each other. R S Q TQ ! !!! RS ! Read: segment TQ perpendicular to segment RS. Use this figure to complete Exercises 3–5. 3. Segment BX is perpendicular to segment BO. Write this with symbols. B C A B O X Y "!# GF " "!# AD I "!# BH ! "!# HE O "!# BH " "!# CE M "!# HG " "!# AB O "!# HE ! "!# CB F "!# HG & "!# BC are skew N D H E G F To solve the riddle, re-arrange the letters for the true boxes. ! BX ! ! BO 4. Find two other line segments that are perpendicular to each other. eggonomics What do hens study in college? Possible answer: ! XY and ! OY 5. What symbol in the figure tells you that line segments are perpendicular to each other? the square corner 35 Copyright © by Holt, Rinehart and Winston. All rights reserved. Holt Mathematics Practice A 8-5 Triangles LESSON Classify each triangle as acute, obtuse, or right. 2. Use the diagram to find the measure of each indicated angle. 3. 60° 70° 90° 30° 60° right 30° 50° acute 5. 2 in. 2 in. 3 in. 6. 5 cm 5 cm 90° 2. "DAC 45° 120° 30° 3. "ABC 90° 4. "EBA 90° 5. "ACB 45° 4 ft D E B 45° 45° C A Classify each triangle using the given information. 6. The perimeter of the triangle is 30 in. 5 ft 5 cm 1. "CBD obtuse Classify each triangle as scalene, isosceles, or equilateral. 4. Holt Mathematics Practice B 8-5 Triangles LESSON 1. 36 Copyright © by Holt, Rinehart and Winston. All rights reserved. 7. The perimeter of the triangle is 15 cm. 8. The perimeter of the triangle is 22 ft. 3 ft isosceles equilateral scalene 10 in. 10 in. 8 ft 5 cm Find the measure of the unknown angle. 7. 8. ? 90° 45° 45° equilateral 35° 50° ? ? 70° 6 ft 3 cm 9. 60° scalene isosceles 9. The angles of a triangular sail measure 90°, 30°, and 60°. Its sides measure approximately 2 feet, 3.5 feet, and 4 feet. Classify the triangular shape of the sail in two different ways. 35° 110° It is a right triangle; It is a scalene triangle. 10. One side of an equilateral triangle measures 4 cm. What are the lengths of the other two sides of the triangle? 10. Two angles in one triangle are congruent to two angles in another triangle. What can you conclude about the third angle in both triangles? They both measure 4 cm. 11. Karen says the angles of her triangle measure 90°, 50°, and 60°. Explain why this is impossible. They are congruent. The sum of those angles is 200°, and the sum of the angles in any triangle is always 180°. Copyright © by Holt, Rinehart and Winston. All rights reserved. 37 Copyright © by Holt, Rinehart and Winston. Holt Mathematics Copyright © by Holt, Rinehart and Winston. All rights reserved. 103 38 Holt Mathematics Holt Mathematics