2 Triangle – 3-sided polygon named using its 3 vertices Triangles are classified in two ways: sides and angles.
3 Angle Classifications All triangles have at least 2 acute angles, the third is used to classify the angle.Acute triangle - 3 acute anglesEquiangular triangle –3 congruent acute anglesObtuse triangle - 1 obtuse angleRight triangle - 1 right angle
4 Example 1Classify each triangle as acute, equiangular, obtuse, or right.A.101°C.B.60°40°60°60°D.90°70°70°
5 Side ClassificationsTriangles are also classified by the number of congruent sides they have.Equilateral triangle - 3 congruent sidesIsosceles triangle – at least 2 congruent sidesScalene triangle – no congruent sides
6 Example 2 Classify each triangle equilateral, isosceles, or scalene. 60°8 in8 in60°60°10 ft6 ft8 ft4 in