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Lesson Plan for Geometry 3.2 What: Geometry lesson When: Week 3 day 2 Who: Rising 9th Graders Essential Questions Content Objectives Skill Objectives Do Now (5 min) Hook/Teaching Point Procedures What makes a logical argument? How can you prove that argument? When does algebra help us understand geometry and when does geometry help us understand algebra? SWBAT use the SSS and SAS Postulates to test for triangle congruence. SWBAT prove that triangles are congruent or similar. SWBAT formulate and test conjectures about the properties and attributes of polygons. Note: Write this up as a hand-out. Draw an acute triangle with angles that measure 44° and 56°. Draw and obtuse triangle with angles that measure 110° and 40°. Draw an isosceles triangle on a line with two angles measuring 75°. For each of the triangles above find the measure of the third angle. What theorem tells you that the sum of the angles in a triangle is equal to 180? Hold two identical objects of your choosing. Ask students: what’s the difference between these two things? Wait for responses. Are they the same? How can you prove it to me? Today we are going to continue our discussion on proofs by learning very common proofs that will enable us to more clearly understand how to form a logical argument in math. We are also going to learn how to write a few different kinds of proofs. 1. If two geometric figures have exactly the same shape and size, they are congruent. (12 min) Today we are going to learn how to prove whether two triangles are congruent Side-Side-Side (SSS) Congruence (p.262-263 – Ex 1, 2) If three sides of one triangle are congruent to the three sides of a second triangle, then the triangles are congruent. Introduce the terminology and the congruence symbol. Do example that is given in the box Write a two column proof for example 1 pg 262 2. Introduce flow proofs: (8min) A flow proof organizes statements in logical order, starting with the given statements. Each statement is written in a box with the reason verifying the statement written below the box. Arrows are used to indicate the order of the statements. Write a two column proof for it Paragraph proof - A kind of proof in which the steps are written out in complete sentences, in paragraph form. Identical in content, but different in form, from a two-column proof. (They will write a paragraph proof on their own) Side-Angle-Side (SAS) Congruence (p. 264-266 – ex 3, 4) If two sides and the included angle of one triangle are congruent to two sides and the included angle of a second triangle, then the triangles are congruent. Example in the book 3. For example 3, whiteout reasons 3 and 5 and have students fill in independently and then discuss together. Then have students write a two column proof for example 4 (the reasons and statements should e the same, just in a different format). (13 min) 4. Kids do a flow proof and paragraph proof (6 min) Write a two column proof Write a flow proof Write a paragraph proof Practice Closing & Assessment Homework (Independent Practice) Paragraph proof – example 4, page 266 Two column proof – example 4 pg 266 Page 267 – 5,6 Have groups share out table by table. Introduce homework. (6 min) p. 267-270 #12-19