 # Section 4.1 Classifying Triangles

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Section 4.1 Classifying Triangles
Geometry Section 4.1 Classifying Triangles

Triangle – 3-sided polygon named using its 3 vertices
Triangles are classified in two ways: sides and angles.

Angle Classifications
All triangles have at least 2 acute angles, the third is used to classify the angle. Acute triangle - 3 acute angles Equiangular triangle – 3 congruent acute angles Obtuse triangle - 1 obtuse angle Right triangle - 1 right angle

Example 1 Classify each triangle as acute, equiangular, obtuse, or right. A. 101° C. B. 60° 40° 60° 60° D. 90° 70° 70°

Side Classifications Triangles are also classified by the number of congruent sides they have. Equilateral triangle - 3 congruent sides Isosceles triangle – at least 2 congruent sides Scalene triangle – no congruent sides

Example 2 Classify each triangle equilateral, isosceles, or scalene.
60° 8 in 8 in 60° 60° 10 ft 6 ft 8 ft 4 in

Isosceles Triangles Leg Leg Base

Example 3 Find the measures of the 3 sides of isosceles triangle KLM with base KL. M 4x - 13 12 - x K L x + 6

Homework Page 239: all