## The Isosceles Triangle Dresser and Me - Section 1: Warm-Up: The Isosceles Triangle Dresser and Me

# Context Problem Practice

Lesson 8 of 11

## Objective: Students will be able to persevere in solving real-world trigonometry problems.

Photographs of real-world situations engage my students. This warm-up provides students with a glimpse of geometry in my real world; it’s a picture of me standing next to an isosceles triangle dresser of approximately the same height. I project the photo for my students and let them ask some questions, some silly, most math related. Ultimately, I give them the approximate length of the base of the dresser (28”) and my height (5’2”) and then pose the following problem for them to solve: **what is the minimum base angle measure that guarantees the dresser will be taller than me?**

As students work on the warm-up, I circulate the room, taking note of the geometric and measurement ideas students bring into the problem:

- the altitude of an isosceles triangle bisects the base as well as the vertex angle
- half the vertex angle and one of the base angles are complementary to one another (which means different trigonometric ratios may be used to correctly solve the problem)
- the dresser’s height must be vertical, i.e., it cannot be the slant height
- the answer must be stated as “greater than” not “greater than or equal to” if the height of the dresser is to exceed my height (
**MP1**).

My students usually volunteer fantastic ideas like these during our whole-class discussion.

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Students may work individually or with a partner to talk to the text as they work on several challenging context problems. In this task, students roll a die to determine which problem they will work on; when they finish working out the problem, they roll the die again to determine the next problem to tackle.

Because the context problems in this task are challenging, I encourage students to check in with other students working on the same problem to share their own interpretations of the problem and how they have decided to tackle it (**MP1**). As I circulate the room, I publicly announce some of my observations like, “I have noticed this pair of students is using a pen, pencil, and eraser to model the position of the lighthouse, boat, and coast guard station” or “I see students using their arms to try to show what the cracked tree might look like.” Sometimes I just call attention to students who reference their notes to correctly interpret “angle of elevation” to continue to spread ideas and resources around the classroom.

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#### Debrief and Exit Ticket

*20 min*

To debrief our work today, I ask students to return to their home group. I ask student groups to start with the problems they have all worked through before discussing any problem that only 1, 2, or 3 students have worked on, to try to come to an agreement on the solution to each problem. If groups cannot come to consensus, they can call me over to listen to the variations in their ideas and facilitate a productive discussion that will bring them to consensus.

Ultimately, **each individual student will reflect on the one problem they thought helped them learn the most and explain why.** Additionally, students may also choose to write down any “notes to self” they want to keep in mind as they continue to learn more about trigonometry. These reflections will ultimately serve as the exit ticket for the day.

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- UNIT 1: Creating Classroom Culture to Develop the Math Practices
- UNIT 2: Introducing Geometry
- UNIT 3: Transformations
- UNIT 4: Discovering and Proving Angle Relationships
- UNIT 5: Constructions
- UNIT 6: Midterm Exam Review
- UNIT 7: Discovering and Proving Triangle Properties
- UNIT 8: Discovering and Proving Polygon Properties
- UNIT 9: Discovering and Proving Circles Properties
- UNIT 10: Geometric Measurement and Dimension
- UNIT 11: The Pythagorean Theorem
- UNIT 12: Triangle Similarity and Trigonometric Ratios
- UNIT 13: Final Exam Review

- LESSON 1: Definition of Similarity and Similar Triangles
- LESSON 2: Similarity Problem Solving and Proofs
- LESSON 3: Similarity Group Assessment
- LESSON 4: Introduction to the Slope Ratio (Tangent)
- LESSON 5: Solve Real World Problems with Clinometers
- LESSON 6: Introduction to Sine and Cosine
- LESSON 7: Problem Solving with Right Triangles and Trig
- LESSON 8: Context Problem Practice
- LESSON 9: The Soda Can Task: Trigonometry and Area Application
- LESSON 10: Review for Trigonometry Unit Assessment
- LESSON 11: Trigonometry Unit Assessment