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Transcript
5.1 Classifying Triangles Classifying Triangles You will learn to identify the parts of triangles and to classify triangles by their parts. In geometry, a triangle is a figure formed when _____ three noncollinear points are connected by segments. D E F Each pair of segments forms an angle of the triangle. The vertex of each angle is a vertex of the triangle. Classifying Triangles Triangles are named by the letters at their vertices. ΔDEF is shown below. Triangle DEF, written ______, vertex angle D The sides are: EF, FD, and DE. The vertices are: D, E, and F. E side F The angles are: E, F, and D. In Chapter 3, you classified angles as acute, obtuse, or right. Triangles can also be classified by their angles. acute angles. All triangles have at least two _____ right obtuse or _____. The third angle is either _____, acute ______, Classifying Triangles acute triangle 60° Triangles Classified by Angles obtuse right triangle 120° triangle 17° 30° 80° 60° 43° 40° 3rd angle is 3rd angle is 3rd angle is acute _____ obtuse ______ right ____ Classifying Triangles scalene isosceles equilateral no ___ sides congruent at least two __________ sides congruent all ___ sides congruent Triangles Classified by Sides Classifying Triangles The angle formed by the congruent sides is called the vertex angle ___________. The two angles formed by the base and one of the congruent sides are called base angles ___________. The congruent sides are called legs. leg leg The side opposite the vertex angle is called the _____. base