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# Using Trigonometric Ratios (Day 1 of 2)

Lesson 4 of 17

## Objective: SWBAT use trigonometric ratios to solve a right triangle.

*50 minutes*

#### Warm-up

*15 min*

At the start of class today, students will have their second attempt at the Quick Quiz - Special Triangle. This will be their last opportunity to re-take this quiz during the class period. My Quick Quiz strategy is described in this video: Special Right Triangles, quick quiz closure.

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#### Finding Angles

*20 min*

Today, I will be using pages 1-25 of the Flipchart-Using Trignometric Ratios Day 1 and 2.pdf to help students recall how to find a missing angle in a right triangle. I break down the implementation of this resource in the Using Trigonometric Ratios Video Explanation of Flipchart.

While presenting page 4 of the flipchart, I plan to talk with my students about finding a good method to remember the trig ratios. Of course, memorizing the phrase Soh Cah Toa is a popular way for students to remember the ratios, but I find that some students don’t actually spell it right so it doesn’t really work for them. I am going to encourage my students to make up a phrase that goes with Soh Cah Toa to help them spell is correctly. Maybe something like, *some old horse caught another horse taking oats away*. (Not appropriate for our students, but this college level acronym made me laugh… *some old hippie caught another hippie tripping on acid. *Perhaps your students will be just as creative!)

I know pages 6-9 of the flipchart seem very basic. I have found that my students often confuse the opposite and adjacent sides of a triangle, so I emphasize to them that the positions of these angles change based on the reference angle.

In my course, calculator use is encouraged. I plan to use pages 13-16 of the flipchart to introduce how to set up our TI-nSpire calculators to calculate angle measurements in degrees. I will not introduce my students to radian angle measurement until the Trig Functions unit.

Finally I will present pages 17-19 of the flipchart as examples of how to find a missing angle given known information. At this time, I will introduce the concept of inverse trig functions and show my students how to use these functions on their calculators.

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#### Closure: Clicker Checks

*15 min*

To close out today's learning and briefly assess which students have met the learning target, I will ask my students to answer the built in clicker questions on pages 20-25 of the Flipchart-Using Trignometric Ratios Day 1 and 2.

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Today, I will assign students Homework 3 - Fundamentals of Trigonometry as homework.

**Teaching Note**: The last section on this homework has not been covered in class yet. We will be reviewing how to find the missing side lengths tomorrow. So, I will likely give students a couple of days to complete this assignment.

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- UNIT 1: Basic Functions and Equations
- UNIT 2: Polynomial Functions and Equations
- UNIT 3: Rational Functions and Equations
- UNIT 4: Exponential Functions and Equations
- UNIT 5: Logarithmic Functions and Equations
- UNIT 6: Conic Sections
- UNIT 7: Rotations and Cyclical Functions
- UNIT 8: Cyclical Patterns and Periodic Functions
- UNIT 9: Trigonometric Equations
- UNIT 10: Matrices
- UNIT 11: Review
- UNIT 12: Fundamentals of Trigonometry

- LESSON 1: What's so special about similar right triangles?
- LESSON 2: Calculator Investigation: Special Right Triangles (Day 1 of 2)
- LESSON 3: Calculator Investigation: Special Right Triangles (Day 2 of 2)
- LESSON 4: Using Trigonometric Ratios (Day 1 of 2)
- LESSON 5: Using Trigonometric Ratios (Day 2 of 2)
- LESSON 6: Clinometer Project (Day 1 of 2)
- LESSON 7: Clinometer Project (Day 2 of 2)
- LESSON 8: Applications of Right Triangle Trig
- LESSON 9: Law of Sines Basics
- LESSON 10: Ambigouous Cases of the Law of Sines
- LESSON 11: Law of Cosines
- LESSON 12: Short Lesson: Quick Clicker Quizzes
- LESSON 13: More on the Laws: Real World Application
- LESSON 14: Trig Jeopardy
- LESSON 15: Fundamentals of Trig Review - Day 1 of 2
- LESSON 16: Fundamentals of Trig Review - Day 2 of 2
- LESSON 17: Fundamentals of Trigonometry Unit Assessment