Download TWS Lesson #1 Lesson Plan Name: Austin Mahlum Date: Day 1

TWS Lesson #1
Lesson Plan
Name: Austin Mahlum
Date: Day 1
Lesson Title: Apply Triangle Sum Properties (Ch 4.1)
Grade Level: 9-12 (usually 10th)
Time Frame: 45 minutes (1 Day)
Materials and Resources: whiteboard, student selection popsicle sticks, scissors, paper, rulers, protractors, pencils, calculators, student math
notebooks, student math textbooks
Management and Safety Issues: None Evident Pre-Lesson
Central Focus and Common Core State Standard(s):
CCSSM:HSG-CO.C.10 Prove theorems about triangles. Theorems include: measures of interior angles of a triangle sum to 180°; base angles of
isosceles triangles are congruent; the segment joining midpoints of two sides of a triangle is parallel to the third side and half the length; the
medians of a triangle meet at a point.
The goal of this lesson is to develop an understanding that regardless of the classification of a triangle two statements will always hold true.
1. The three interior angles will add up to 180 degrees. 2. An exterior angle of a triangle is equal to the sum of the measures of the two
nonadjacent interior angles.
Mathematical Objectives:
The student will discern and select appropriate classifications of a triangle given said triangle in the homework.
The student will solve for a third interior angle of a triangle given either the other two interior angles or one interior angle and one exterior angle
of a triangle in the homework.
The student will investigate the relationship between an exterior angle of a triangle and the interior angles of said triangle during the in class
activity.
Assessment:
Formative:
Assessment for this lesson will take many different forms.
1. During the launch activity, I will be able to see what their background understanding of triangles is and how that will shape my time
distribution during the lesson.
2. During the entire lesson I will be using a popsicle stick selection method (Math Formative Assessment book #44) for choosing students at
random. I will attempt to use wait time to allow students to think through the question.
3. After the explanation of interior and exterior angles, I will use the examples/non-examples strategy (Math Formative Assessment book #13)
to see how well they understand the terminology.
4. The thumbs up/thumbs down strategy (Math Formative Assessment book #63) at the end will give me key information for teaching this
lesson in the future.
5. Homework: pg. 221 # 1-36 all.
Summative:
At the end of chapter 4, there will be a summative test (or students have the option of an individualized proof project).
Accommodations/Differentiations:
Students of all learning styles should be engaged in the hands-on activities that are embedded in this lesson. Individual situations may arise
where I need to accommodate/differentiate on the fly, but I am excellent at improvisation and can adjust my lesson as necessary. IEP’s are in
place for two students so I must follow that protocol if the situation arises.
Student Needs/Misconceptions:
The students should be able to correctly use a protractor to measure the angles of a triangle (they then should be able to classify the angle). The
student should be able to use angle relationships. The student also must be able to work with the distance formula as well as being able to
calculate the slope of a line given two endpoints on the line. Finally, students must be proficient at solving linear equations.
I anticipate that some students may forget that once we solve for a variable (say x) that we need to plug it back into the original equation of the
angle to find out what the exact angle is.
Academic Language and Mathematical Discourse:
This lesson introduces a lot of vocabulary that students may not have seen before. It will be critical to define and explain the definitions with the
utmost precision as a simple misunderstanding of a definition will result in n-fold mistakes as we continue onward with this unit.
Students will be engaged in the highest level of mathematical discourse when we are doing the second investigation to unlock the exterior angle
theorem.
Lesson Plan:
Launch:
Ask students by a show of hands which shape would provide the most strength to a structure (a square, a triangle, or a circle). A small
amount of discussion amongst the students is appropriate here. Once they figure out that a triangle provides the strongest support, ask them
what they remember about triangles. Compile a short list (have the students come up and write on the board if they would like) on the board
for them to get reacquainted with triangles. Tell the students that today we are going to be focusing on the angles that a triangle has and the
relationships between them.
Explore:
1. Define and explain both interior and exterior angles. Use the example/non-example formative assessment classroom technique to
assist conceptual understanding.
2. Start investigation (1). Model the process and have students follow along. Draw a triangle (classification does not matter) using a
ruler and a sheet of paper, then cut out the triangle. Label the interior angels A, B, and C. Tear off each angle and arrange them
adjacently along the edge of another sheet of paper. Discuss what observations the students have.
3. Give a formal definition of the triangle sum theorem. Then provide an example using the theorem.
4. Start investigation (2). Model the process and have students follow along. Draw a triangle with a “tail” (an extension of one of the
sides). Using a protractor, measure the outside obtuse angle formed by the extension. Measure the interior angles not adjacent to
the exterior angle. Let the students know that sometimes these two interior angles are called remote interior angles. Fill in a chart
on the chalkboard with three sections: 1. Exterior angle 2. One interior angle 3. The other interior angle. Have students discuss what
they see.
5. Give a formal definition of the exterior angle theorem. Then provide an example using the theorem.
6. Go through triangle classification vocabulary. Then work through an example of classifying a triangle.
7. Explain what a corollary to a theorem is and then give a formal definition of the corollary to the triangle sum theorem.
8. Provide an example of the corollary to the triangle sum theorem.
9. Introduce homework for the next day.
10. Spend whatever remains of the rest of the class period working through homework with them.
Summarize:
I anticipate the lesson taking quite a lot of time, so my ending formal assessment should be pretty short. I will have students put their heads
down on the desk and give me an answer to the question “How helpful were the investigation activities in understanding the two main theorems
we had” by giving me either a thumbs up or thumbs down or somewhere in between.
Reflection:
The biggest factor I will likely have to reflect on is time distribution and how much time is needed for each activity. This lesson may teeter on
needing to be split up into two lessons or at least one and a half lessons. Also I should be paying attention to if the students thought the
investigation activities were helpful in understanding the main two theorems.