Lesson 10
1. Lesson 10
1.7. Explore 3
Module 2: Logic and Geometry
Read “Example 2: Reasoning about congruency to prove that sides are equal” and “Example 3: Reasoning about congruency to prove that angles are equal” on pages 109 and 110 of your textbook. As you read over the solutions, consider the following questions.
- How is deductive reasoning used to prove that the triangle is isosceles in Example 2?
- What characteristics of an isosceles triangle were required to build the proof?
- Why did each pair of triangles first have to be proven congruent before the students could prove that
is isosceles and that ∠A = ∠E?
Example 2 shows that it is helpful to keep in mind what it is you are trying to prove when building your proofs. For instance, to prove that the triangle is isosceles, you have to understand what characteristics make a triangle isosceles: two congruent sides and two congruent angles. These then become the parts you have to prove.
Self-Check 3
1. Complete “Your Turn” on page 109 of your textbook. Answer
2. Complete “Your Turn” on page 110 of your textbook. Answer
3. Complete “Practising” questions 4, 5, and 6 on page 113 of your textbook. Answer