Teacher's Guide: Geometry Lesson Plan on Types of Triangles

January 28th, 2007 9th and 10th Grade
25 students 1 IEP student 2 GSSP students
Subject: Geometry Major Content: Types of Triangles
Lesson Length: 50 minutes
Unit Title: Properties of Triangles and other 2-dimensional objects
Lesson Number and Title: #2 Types of Triangles

Context
The main goal of the previous lesson of this unit, the current lesson, and a few lessons in the future is to build our way up to be able to write proofs that show why two triangles are congruent. Before we even get that far, the students must be familiar with the different types of triangles and the many different terms and properties associated with triangles. In this lesson, I will describe to the students the types of triangle that they will encounter in geometry. I will describe the equilateral, isosceles, scalene, and right triangle. The previous lesson was on the definitions and basic facts on the parts that make up triangles (angles, hypotenuse, legs) With this lesson the class will go a little more in depth with those definitions, by finding out what those individual parts can do to change the type of a triangle.
In this class, there is a student with a learning disability that may need some additional explanation of the lesson on a one-to-one basis after the lecture has finished. Also there is one student who has shown signs that he may be exceptional at mathematics, and he may be looked at to be moved into an honors class next year.

Objectives
1. The students should be able to know the types of triangles and be able to explain their properties. Also, the students should be able to identify the differences between the three major types of triangles. They should be able to identify the differences and similarities between the right triangle and the other three major types.
2. The students should be able to look at three-dimensional objects (given the dimensions) and make an accurate guess to what type of triangle form that the shape would fall under.
Connections
MA-HS-3.4.1
Students will identify definitions, axioms and theorems, explain the necessity for them and give examples of them.
MA-HS-3.1.9
Students will classify and apply properties of three-dimensional geometric figures.
Assessment Plan
Objective Number Type of Assessment Description of Assessment Depth of Knowledge Level Adaptations and/or Accommodations
#1 Worksheet A small in-class worksheet that asks students to define keys terms and label each triangle shown as equilateral, isosceles, scalene, and if applicable label it as a right triangle as well. Simply identifying the basic terms of what we covered in class. If a student needed help or more time they could ask for an additional explanation and/or finish it at home.
#2 In-class vote on visual objects I will hold up or show pictures of three-dimensional objects and as a class the students will be able to vote for what type of triangle the example falls under. The vote will occur with the students eyes closed so that they are not persuaded by the majority of the class. If certain students are not responding or unsure of themselves, I will call on them to give their answer before I reveal the correct answer. Students should be able to apply their knowledge of triangles to three-dimensional objects eventually leading them to answering applicable word problems dealing with triangles. If there is a student with vision problems, I will give them a chance to get a closer look or a feel of the object and make a conjecture of their own.

Resources, Media, and Technology
Used a website to come up with a picture of the Louvre Pyramid in France:
http://www1.cs.columbia.edu/~sedwards/photos/paris2002/Images/P3021302%20Louvre%20Pyramid.jpg

Procedures
The class will start with students asking me to do any problems on the board from yesterday's homework. I will try and cover all of the main points from yesterday's lesson in answering the students' questions. If no questions are asked, I will do a very brief (5min.) review of yesterday's material before covering today's lesson. I will explain the types of triangles one by one, but I will save the right triangle for last. During my explanation for each type of triangle, I will keep bringing up yesterday's lesson topics (dealing with the properties of triangles) to help explain the differences and similarities between the parts of these different types. I will go into detail on each triangle and pose questions throughout my lecture to the students to continue reminding them things like what the hypotenuse is and how many degrees total do the angles of a triangle add up to. And after explaining all the types of triangles, I will go back over them one more time quickly to see how much the students retained from my lecture. I will give them a few examples of the dimensions of a triangle and see if they can correctly identify the type of triangle I am talking about. Next, I will hold up some three-dimensional objects in the classroom (piece of pizza, paper cut-outs, architecture in the room) and give them the dimensions for the objects and have an in-class vote on the type of triangle that it is. I will also show them a picture of a work of art from the art museum the Louvre in Paris. It will provide an example of the pitfalls of guessing what type of triangle something is without knowing the dimensions of it. Even though it looks like an equilateral triangle, it is not. Finally, I will give the students a quick in-class assignment to turn in at the end of class. There will also be a homework assignment to be turned in for the following day.