1. Lesson 4-5: Isosceles & Equilateral Triangles Vocab Legs Base Angles Equiangular Bisects The congruent sides of an isosceles ∆ Congruent angles opposite the legs of an isosceles ∆ A triangle with all three angles congruent (all 60 0 ) – also equilateral Cuts into 2 equal pieces

2. Isosceles Triangle leg base base angles Legs are congruent Base angles are congruent If we know 1 angle, we can find the rest Always start by identifying base angles and legs! If one is true, the other must be true!

3. Example 6-2e Answer: A Multiple-Choice Test Item If and what is the measure of A. 25 B. 35 C. 50 D. 130 Mark given information first Identify legs & base angles Use angle relationships

4. Equilateral Triangles A special type of isosceles triangle All sides and angles are congruent Also called equiangular All angles must be 60 0

5. a. Find x. Example 6-4d b. Answer: 90 Answer: 30  ABC is an equilateral triangle. bisects