2-3: Proving Theorems

Reasons used in Proofs

• Given information• Definitions• Postulates (Algebraic Properties included)• Theorems that have already been proved

• Theorem 2-1: The Midpoint Theorem– If M is the midpoint of AB, then AM = ½ AB and

MB = ½ AB

Let’s Look at Proof on page 43

• Theorem 2-2: The Angle Bisector Theorem– If ray BX is the bisector of <ABC , then m < ABX = ½

m <ABC and m <XBC = ½ m < ABCProve on your own

• Look at Example 2 on page 44

Classwork

• Pg 45: 1-10 together

Homework

• Pg 46: 1-8, 10-18, 19• study for quiz over 2.1-2.3