Lesson Plan


Teacher:  Kerri Bernhardt                                                      Lesson Topic:  Triangle Congruence SSS & SAS


Grade Level: 10th grade                                                        Date Taught:            


NCSCOS Goal and Objective(s):  Mathematics-The students will learn how to prove two triangles congruent using multiple postulates and theorems. (NCSCS 2.03 a) Computer- The students will use spreadsheets to solve problems and display data. (NCSCS 3.02)


Prerequisite Background Knowledge/Preassessment (information needed for students to benefit from lesson):

The students will need to know what congruent means and properties that can be used to prove triangles are congruent.


Materials/Resources/Technology: Straws, paper, writing utensil, textbook, computer lab with spreadsheet application, projector


Procedures (beginning, middle, end comprehensive step-by-step explanation of teacher and student activities):

The lesson will begin with an investigation activity of the SSS postulate.  The students will use straws to make triangles with sides of 2, 3, and 4 inch sides.  They will compare triangles with other students.  Next they will make a conjecture about two triangles in which three sides of one triangle are congruent to three sides of the other triangle.  Next they will support their conjecture using three other lengths to make a different triangle and comparing with other students.  At the end we will discuss the activity and what students found.

We will talk about corresponding parts of congruent triangles.  We will also discuss how we do not need all 6 parts to prove congruence but just three sides.  The students will help me write the SSS postulate from the activity.  We will use a picture of a bridge with two girders marked then the students will try to prove congruence.  A proof can be written using the SSS postulate.

Next we are going to do another activity where students spread their arms a certain measured distance then move their arms somewhere else to see if the distance is the same (thus creating congruent triangles).  The activity will be done in pairs with one person making the triangle while the other measures then swapping.  The students will make conjectures then we will use that activity to discuss the SAS postulate.  The students will help me write the SAS postulate from the activity.  We will develop two proofs using the SAS postulate. 

            Finally the class will travel to the computer lab and use a spreadsheet application to compare side and angle data of different triangles to determine if they are congruent.      
Higher Order Thinking Question:  What is the order of the steps in proving the Side Angle Side postulate?

Differentiation (What will the teacher do to meet the needs of the various learners in your class?):

The investigation activities helps the students visualize the SSS and SAS postulate.  The computer activity gives another method to review what was learned from the lesson.


Assessment (How will the teacher know students learned?):

The computer activity will be collected and assessed to determine students understanding.


Remediation/Next Steps (What will the teacher do for students who did not meet expectations? Also, what will the students do for follow-up/Homework/Enrichment?):

Students who did not meet expectations will be given another assignment of problems and written explanations after a review of the topics covered.  All students will be assigned a number of homework problems to ensure their understanding.


Reflection - (Was the lesson successful? What should be done differently regarding classroom management, instructional presentation, etc.?):

Kerri Bernhardt:  Back