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Proving Theorems 2-3.

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Presentation on theme: "Proving Theorems 2-3."— Presentation transcript:

1 Proving Theorems 2-3

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9 Write a two-column proof
EXAMPLE 1 Write a two-column proof Write a two-column proof GIVEN: m∠ 1 = m∠ 3 PROVE: m∠ EBA = m∠ DBC STATEMENT REASONS 1. m∠ 1 = m∠ 3 1. Given 2. m∠ EBA = m∠ m∠ 2 2. Angle Addition Postulate 3. m∠ EBA = m∠ m∠ 2 3. Substitution Property of Equality

10 Write a two-column proof
EXAMPLE 1 Write a two-column proof 4. m∠ m∠ 2 = m∠ DBC 4. Angle Addition Postulate 5. m∠ EBA = m∠ DBC 5. Transitive Property of Equality

11 GUIDED PRACTICE for Example 1
1. Four steps of a proof are shown. Give the reasons for the last two steps. GIVEN : AC = AB + AB PROVE : AB = BC STATEMENT REASONS 1. AC = AB + AB 1. Given 2. AB + BC = AC 2. Segment Addition Postulate 3. AB + AB = AB + BC 3. ? 4. AB = BC 4. ?

12 GUIDED PRACTICE for Example 1 ANSWER GIVEN : AC = AB + AB
PROVE : AB = BC ANSWER 1. AC = AB + AB 2. AB + BC = AC 3. AB + AB = AB + BC 4. AB = BC Given Segment Addition Postulate Transitive Property of Equality Subtraction Property of Equality STATEMENT REASONS

13 EXAMPLE 2 Name the property shown Name the property illustrated by the statement. a. If R T and T P, then R P. b. If NK BD , then BD NK . SOLUTION Transitive Property of Angle Congruence a. b. Symmetric Property of Segment Congruence

14 GUIDED PRACTICE for Example 2 2. CD CD Reflexive Property of Congruence ANSWER 3. If Q V, then V Q. Symmetric Property of Congruence ANSWER

15 EXAMPLE 3 Use properties of equality Prove this property of midpoints: If you know that M is the midpoint of AB ,prove that AB is two times AM and AM is one half of AB. GIVEN: M is the midpoint of AB . PROVE: a. AB = 2 AM b. AM = AB 2 1

16 Use properties of equality
EXAMPLE 3 Use properties of equality STATEMENT REASONS 1. M is the midpoint of AB. 1. Given 2. AM MB 2. Definition of midpoint 3. AM = MB 3. Definition of congruent segments 4. AM + MB = AB 4. Segment Addition Postulate 5. AM + AM = AB 5. Substitution Property of Equality

17 Use properties of equality
EXAMPLE 3 Use properties of equality 6. 2AM = AB a. 6. Distributive Property AM = AB 2 1 7. b. 7. Division Property of Equality

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19 EXAMPLE 4 Solve a multi-step problem Walking down a hallway at the mall, you notice the music store is halfway between the food court and the shoe store. The shoe store is halfway between the music store and the bookstore. Prove that the distance between the entrances of the food court and music store is the same as the distance between the entrances of the shoe store and bookstore. Shopping Mall

20 EXAMPLE 4 Solve a multi-step problem SOLUTION STEP 1 Draw and label a diagram. STEP 2 Draw separate diagrams to show mathematical relationships. STEP 3 State what is given and what is to be proved for the situation. Then write a proof.

21 Solve a multi-step problem
EXAMPLE 4 Solve a multi-step problem GIVEN: B is the midpoint of AC . C is the midpoint of BD . PROVE: AB = CD STATEMENT REASONS 1. B is the midpoint of AC . C is the midpoint of BD . 1. Given 2. AB BC 2. Definition of midpoint 3. BC CD 3. Definition of midpoint

22 Solve a multi-step problem
EXAMPLE 4 Solve a multi-step problem 4. AB CD 4. Transitive Property of Congruence 5. AB = CD 5. Definition of congruent segments


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