Triangles Lesson 10-4

Triangle A triangle is a figure that has 3 sides and 3 angles. The sum of the measure of the angles is 180° m<1 + m<2 + m<3 = 180° 1 2 3

Find the missing angle measure <1 = 50° <2= 75° <3 = ?

Find the missing angle measure <1 = 50° <2= 75° <3 = ? 50 + 75 = 125 180 – 125 = 55°

Classify Triangles Using Angles Acute Triangle Properties: All acute angles.

Classify Triangles Using Angles Right Triangle Properties: 1 right angle.

Classify Triangles Using Angles Obtuse Triangle Properties: 1 obtuse angle.

Classify Triangles Using Sides Scalene Triangle Properties: No congruent sides.

Classify Triangles Using Sides Isosceles Triangle Properties: At least 2 congruent sides. This symbol represents that the sides are congruent.

Classify Triangles Using Sides Equilateral Triangle Properties: 3 congruent sides.

Naming Triangles Triangles have a 2 part name. The first part of the name, names the angles (acute, obtuse, or right) The second part of the name, names the sides (scalene, isosceles, or equilateral) Example: Obtuse Scalene

Name the Triangle Acute Scalene

Name the Triangle Right Scalene

Name the Triangle Acute Equilateral

Find the missing angle. Then classify the triangle as acute, right, or obtuse. x 40°

Find the missing angle. Then classify the triangle as acute, right, or obtuse. 20° 25° x

Find the missing angle. Then classify the triangle as acute, right, or obtuse. 30° x 130°

Don’t Forget Class Assignment: Homework: Old Blue p. 588 - Lesson 10-4 Old Blue - read p. 428-429; complete p. 430-431 (1-28) IXL Lesson P7 (minimum 80%) Homework: Old Blue p. 588 - Lesson 10-4