Download Lesson Plan for Geometry 3.2

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