Download Lesson 4.1, 4.5, Congruent, Isosceles, and Equilateral Triangles

Lesson 4.1: Triangle Congruency
Speaking in Math
• Naming angles on a triangle:
• Congruent Sides and Angles:
• Ex: For △ABC ≅ △XYZ,
∠A ≅
∠C ≅
BC ≅
Practice
Given: △DEF ≅ △XYZ.
∠E ≅
∠F ≅
DE ≅
If DE = 5x – 12 and XY = 3x + 8, what is the length of
DE?
Practice
• Name both pairs of congruent angles and sides for
the two triangles:
A
C
B
D
Lesson 4.5 – Isosceles and
Equilateral Triangles
Triangles by angle
• Acute:
• Right:
• Obtuse:
Practice
• Classify each triangle by angle. Figures not to scale.
60o
6x – 20
16x
14x + 40
4x
80o
Triangles by Side Length
• Scalene:
• Isosceles:
• Equilateral:
Isosceles Triangles
• Vertex angles:
• Base angles:
• Ex: Right isosceles triangle.
Practice
• One angle of an isosceles triangle is 110o. What are
the measures of the other two angles?
• What is the value of the vertex angle?
8x
5x + 40

Practice
• What is the measure of each angle of an equilateral
triangle?
• Sides of an isosceles triangle.
Classwork
• Lesson 4.1, #1 – 6
Lesson 4.5, #1 – 5
Homework
• Lesson 4.1, #23 – 37 odd
• Lesson 4.5, #7 – 19 odd