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Writing Proofs. During this lesson, you will: Write reasons for statements Write simple geometric proofs using properties of equations. Recall: Properties of Equations. Addition: If a = b, then a + c = b + c , for all real numbers a, b, and c.
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Writing Proofs During this lesson, you will: Write reasons for statements Write simple geometric proofs using properties of equations
Recall: Properties of Equations Addition:If a = b, then a + c = b +c, for all real numbers a, b, and c. Subtraction: If a = b, then a - c = b - c, for all real numbers a, b, and c. Multiplication:If a = b, then a ∙ c = b ∙ c, for all real numbers a, b, and c. Division: If a = b, then a/c = b/c.
Example1 What reason can you give for the following conclusion? If m ∠ AOB = m ∠ COD, then m ∠ AOB + m ∠ BOC = m ∠ BOC + m ∠ COD ? Addition Property of Equality
Example2 What reason can you give for the following conclusion? If 2 (m ∠P )= 80, then m ∠P = 40. Division Property of Equality
Example 3 What conclusion can you draw based upon the given information? Give a reason for each statement. Given.
Example4 Write a complete proof of the following: Given: m ∠ x = 38; m ∠ y = 38 Prove: x y
Example5 Give a reason for each step in the proof on the following slide. Given: m ∠AOB + m∠ BOC = m ∠BOC + m ∠ COD Prove:∠ AOB ∠ COD
Example6 1. Draw and label a diagram based upon the given information. 2. Write the missing statements in the proof on the following slide. Directions:
Given: AB ≅ BC, BC ≅ CD, AB = 21Prove: CD = 21 Diagram: A B C D
Final Checks for Understanding On the following slide, statements in the first column are given information. Use these to draw logical conclusion, then justify your reason for each corresponding conclusion.
HOMEWORK ASSIGNMENT Writing Simple Geometric Proofs WS