4.7.1 USE ISOSCELES AND EQUILATERAL TRIANGLES

Chapter 4: Congruent Triangles

SWBAT:Define Vertex angle, leg, base, and base angle. State, prove, and use the base angle theorem and converse

You will accomplish this on slide 5 and on homework problems

Isosceles Triangles

We know SAS and ASA so for Isosceles Triangles we have many possiblities.

Certain theorems can state short cuts for us for when we are proving triangles that are Isosceles congruent.

Vocab:

Legs: two sides of an Isosceles triangle that are congruentBase: the side of an Isosceles triangle that is not

congruent to the other twoBase angles: the two angles that are congruent in an

Isosceles triangleVertex angle: the third angle that is not congruent to the

other two Vertex Angle

Base

Legs

Base Angles

Isosceles Triangle:

Base Angle Theorem:If two sides of a triangle are congruent then the two

angles opposite them are congruentConverse of the Base Angle Theorem:If two angles of a triangle are congruent then the

two sides opposite them are congruentGiven: Then: Given: Then:

Measurement

Given ABC and ABE are Isosceles TrianglesGiven mACB = 10⁰And AB AC AEFind x and y ifm AEB = (3x – y) ⁰m BAE = (6x + 2y) ⁰

A

B

C

D

E

Homework

P. 2671 – 6, 12, 13, 15, 19, 26, 41, 48