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Transcript
9-6 Classifying Triangles Preview Warm Up California Standards Lesson Presentation Holt CA Course 1 9-6 Classifying Triangles Warm Up 1. What is the name of a six-sided polygon? hexagon 2. What is the definition of an acute angle? an angle that measures less than 90° 3. The measure of one of two supplementary angles is 32°. What is the measure of the other angle? 148° Holt CA Course 1 9-6 Classifying Triangles California Standards Preparation for MG2.3 Draw quadrilaterals and triangles from given information about them (e.g., a quadrilateral having equal sides but no right angles, a right isosceles triangle.) Holt CA Course 1 9-6 Classifying Triangles Vocabulary scalene triangle isosceles triangle equilateral triangle acute triangle obtuse triangle right triangle Holt CA Course 1 9-6 Classifying Triangles One way to classify triangles is by the lengths of their sides. Triangles classified by sides A scalene triangle has no congruent sides. Holt CA Course 1 9-6 Classifying Triangles One way to classify triangles is by the lengths of their sides. Triangles classified by sides An isosceles triangle has at least 2 congruent sides. Holt CA Course 1 9-6 Classifying Triangles One way to classify triangles is by the lengths of their sides. Triangles classified by sides In an equilateral triangle, all of the sides are congruent. Holt CA Course 1 9-6 Classifying Triangles One way to classify triangles is by the lengths of their sides. Another way is by the measures of their angles. Triangles classified by angles In an acute triangle, all of the angles are acute. Holt CA Course 1 9-6 Classifying Triangles One way to classify triangles is by the lengths of their sides. Another way is by the measures of their angles. Triangles classified by angles An obtuse triangle has one obtuse angle. Holt CA Course 1 9-6 Classifying Triangles One way to classify triangles is by the lengths of their sides. Another way is by the measures of their angles. Triangles classified by angles A right triangle has exactly one right angle. Holt CA Course 1 9-6 Classifying Triangles Additional Example 1: Classifying Triangles Classify each triangle according to its sides and angles. A. isosceles Two congruent sides acute Three acute angles This is an isosceles acute triangle. B. scalene right No congruent sides One right angle This is a scalene right triangle. Holt CA Course 1 9-6 Classifying Triangles Additional Example 1: Classifying Triangles Classify each triangle according to its sides and angles. C. equilateral Three congruent sides acute Three acute angles This is an equilateral acute triangle. D. scalene right No congruent sides One right angle This is a scalene right triangle. Holt CA Course 1 9-6 Classifying Triangles Check It Out! Example 1 Classify each triangle according to its sides and angles. A. isosceles Two congruent sides obtuse One obtuse angle This is an isosceles obtuse triangle. B. isosceles right Two congruent sides One right angle This is an isosceles right triangle. Holt CA Course 1 9-6 Classifying Triangles Check It Out! Example 1 Classify each triangle according to its sides and angles. C. scalene obtuse No congruent sides One angle exceeding 90° This is a scalene obtuse triangle. D. scalene obtuse No congruent sides One angle exceeding 90° This is a scalene obtuse triangle. Holt CA Course 1 9-6 Classifying Triangles Additional Example 2: Identifying Triangles Identify the different types of triangles in the figure, and determine how many of each there are. Holt CA Course 1 Type How many Name Scalene 2 ABD, CBD Isosceles 2 ACE, ABC Right 2 ABD, CBD Obtuse 1 ACE Acute 1 ABC 9-6 Classifying Triangles Check It Out! Example 2 Identify the different types of triangles in the figure, and determine how many of each there are. A I B J C D H G Type Isosceles 5 Name DJA, JDG HJI, BCD DFE F Holt CA Course 1 How many E Obtuse 2 DJA, ADG Acute 4 JDG, JHI, BCD, DEF 9-6 Classifying Triangles Lesson Quiz Classify each triangle according to its sides or angles. 1. 7 ft, 8 ft, 12 ft scalene 2. 45°, 90°, 45° right 3. 12, 9, 12 isosceles 4. 120°, 20°, 40° obtuse 5. Identify the different types of triangles in the figure, and determine how many of each there are. 1 isosceles acute triangle, 1 equilateral triangle, 1 scalene right triangle Holt CA Course 1