Lesson 6: 4-6: Isosceles and Equilateral Triangles

1. What makes a triangle isosceles?
2. How can you use the properties of isosceles and equilateral triangles to set up an algebraic equation to solve for a given variable?

Legs of an Isosceles Triangle
Vertex Angle
Base Angles

G.CO.10
Prove theorems about triangles.
G.CO.12
Make formal geometric constructions with a variety of tools and methods (compass and straightedge, string, reflective devices, paper folding, dynamic geometric software, etc.)

https://docs.google.com/document/d/1Wi6oBP9pbwdBW1CPr4x4vVBOYkSXVKTdszWiPd1Ccm4/copy?usp=sharing

Isosceles triangles have special properties recognized in the Isosceles Triangle Theorem and its converse. If two sides of a triangle are congruent, the the angles opposite those sides are congruent. This theorem is used to prove corollaries about the angles of an equilateral triangle.

Engineers design roller coasters with triangular reinforcements between the tracks. This design lends support and stability.

Students approaching grade level can be given practice problems in small groups to work with other students or directly with the teacher.
Students beyond grade level can make deeper connections to the properties by working on problems with more complex algebraic connections.

Formative Assessment

Textbook in class

Access online textbook and resources through class link.