11.2 Triangles. Unlock the Problem. Math Talk Math Talk. Essential Question. Name. Module

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1 ? Name 11.2 Triangles Essential Question How can you classify triangles? Geometry and Measurement 5.5. MTHEMTIL PROESSES 5.1.F, 5.1.G Unlock the Problem If you look closely at Epcot enter s Spaceship Earth building in Orlando, Florida, you may see a pattern of triangles. The triangle outlined in the pattern at the right has 3 congruent sides and 3 acute angles. What type of triangle is outlined? omplete the sentence that describes each type of triangle. lassify triangles by the lengths of their sides. lassify triangles by the measures of their angles. n equilateral triangle has _ congruent sides. right triangle has one 90, or angle n isosceles triangle has _ congruent sides. 2 in. n acute triangle has 3 angles scalene triangle has _ congruent sides. 5 in. 4 in. n obtuse triangle has 1 angle Houghton Mifflin Harcourt Publishing ompany The type of triangle outlined in the pattern can be classified by the length of its sides as an triangle. The triangle can also be classified by the measures of its angles as an triangle. Math Talk Math Talk Is an equilateral triangle also a regular polygon? Explain. Module

2 ctivity Hands lassify triangle by the lengths of its sides and by the measures of its angles. On Materials centimeter ruler protractor STEP 1 Measure the sides of the triangle using a centimeter ruler. Label each side with its length. lassify the triangle by the lengths of its sides. What type of triangle has 3 sides of different lengths? What is an angle called that is greater than 90º and less than 180º? STEP 2 Measure the angles of the triangle using a protractor. Label each angle with its measure. lassify the triangle by the measures of its angles. Triangle is a triangle. Try This! raw the type of triangle described by the lengths of its sides and by the measures of its angles. Scalene Triangle by Length of Sides Isosceles Triangle by ngle Measure Obtuse cute 416 Think: I need to draw a triangle that is acute and scalene. Math Talk an you draw a triangle that is right equilateral? Explain. Houghton Mifflin Harcourt Publishing ompany

3 Name Share and Show lassify each triangle. Write isosceles, scalene, or equilateral. Then write acute, obtuse, or right ft 51 9 ft ft cm 29 Problem Solving 4. an you tell that a triangle is obtuse, right, or acute without measuring the angles? Explain. 5. Multi-Step raw 2 equilateral triangles that are congruent and share a side. What polygon is formed? Is it a regular polygon? Houghton Mifflin Harcourt Publishing ompany Image redits: (br) Wim Wiskerke/lamy; (bl) rthur Tilley/Open oor Images/Jupiterimages/Getty Images Problem Solving 6. nalyze Shannon said that a triangle with exactly 2 congruent sides and an obtuse angle is an equilateral obtuse triangle. escribe her error. lassify the triangles in the structures below. Write isosceles, scalene, or equilateral. Then write acute, obtuse, or right Module 11 Lesson 2 417

4 aily ssessment Task Fill in the bubble completely to show your answer. 9. Ricky drew a triangle with angles measuring 90, 30, and 60, and no congruent sides. Which of these describes the triangle? isosceles right equilateral obtuse scalene acute scalene right 10. Which of these triangles is isosceles and obtuse? 11. Multi-Step Jenna drew this triangle, and then drew the dotted line down the center. What type of triangle did she draw first? What triangles resulted from the dotted line? right; two scalene obtuse triangles equilateral; two right triangles scalene right; two right triangles 6 cm 6 cm 3 cm 3 cm 6 cm isosceles acute; two equilateral triangles TEXS Test Prep 12. Which kind of triangle has exactly 2 congruent sides? isosceles equilateral scalene right 418 Houghton Mifflin Harcourt Publishing ompany

5 Homework and Practice Name Geometry and Measurement 5.5. MTHEMTIL PROESSES 5.1.F, 5.1.G 11.2 Triangles lassify each triangle. Write isosceles, scalene, or equilateral. Then write acute, obtuse, or right ircle the figure that does not belong. Explain. 7. Houghton Mifflin Harcourt Publishing ompany Problem Solving 8. Parker drew a triangle with no congruent sides and a 95 angle. lassify the triangle by the lengths of its sides and measures of its angles. Explain. Module 11 Lesson 2 419

6 Lesson heck Fill in the bubble completely to show your answer. 9. Lindsay draws a right triangle and adds the measures of the right angle and one acute angle. Which is a possible sum of the two angles? TEXS Test Prep 10. Which of these triangles is isosceles and acute? Which kind of triangle has 3 congruent sides? right isosceles equilateral scalene 12. Which of the following is another way to classify a scalene triangle with one angle greater than 90? acute obtuse right equilateral 13. Multi-Step Mrs. ennett has a rug that is an equilateral triangle with a perimeter of 12 feet. Which could be the lengths of the sides of the rug? 14. Multi-Step Nathan cut a square tile in half for his kitchen floor design. He made one cut along a diagonal from one vertex to another vertex. Which triangles resulted from the cut? 4 ft, 4 ft, 4 ft two scalene right triangles 5 ft, 5 ft, 2 ft two isosceles obtuse triangles ft, 3 ft, 3 ft 3 ft, 4 ft, 5 ft two isosceles right triangles two equilateral right triangles Houghton Mifflin Harcourt Publishing ompany