Teaching Students About the Many Properties of Triangles

Context

This is the sixth section of the chapter and the eighth lesson of the unit. Students will need to recall what an isosceles triangle is and be able to identify the bases, legs, and hypotenuses of several different triangles. In this lesson, students will need to find the missing angles and sides of triangles. They must use their Algebra skills to solve for x in many cases. To find the missing angles they will need to know the theorems covered in this section. Also in this section one additional triangle congruence postulate will be given.

Objectives

Students should be able to find missing angles of triangles using basic theorems from this section.

Students should be able to prove triangles are congruent using the hypotenuse-leg theorem.

Resources, Media and Technology

Computer Projector

Computer math program: http://www.mathopenref.com/congruenthl.html

Procedures

Check homework and give out answers to the homework.Answer Questions.

Students take quiz.Proceed into today's lesson.Review isosceles triangle and base. Ask individual students to recall the parts of an isosceles triangle.

Define base and vertex angle.Have students help explain the base angle theorem to the rest of the class. Draw the diagram on the board and ask someone what they think the base angle theorem says when dealing with an isosceles triangle. Do the same with the equiangular corollaries. I will work out a couple of quick examples on the board.

Next have the students work out a couple of examples on their own. They must find the missing angles of a triangle given some information about the triangles. I will go around the room checking everyone to make sure they can work out the problem.The first problem on the board that I do I will do it by myself. After that, I will call on students to see how they worked out the problem.

After we have covered the first part of the section sufficiently, I will move onto the Hypotenuse-Leg Congruence Theorem. I will have some of the information on this theorem already written on the board.

I will use a program off the compute to demonstrate an example of the HL-Theorem. I will ask someone what postulate proves these two triangles congruent. They will use their knowledge of triangle congruence postulates and say that they aren't congruent. That is when I will give them the theorem that only works with right triangles. I will quickly demonstrate the theorem on the computer. I will explain it more formally by drawing diagrams on the board and presenting the theorem. I will do a quick example and then I will call on students to answer questions about another similar example. If time permits, I will do a couple more examples that involve everything that we covered in this lesson. If not, I will assign the homework for the night and remind them of the upcoming test.The students will work on their homework until the end of class.