Unit 49: Right-Triangle Trigonometry

Day 14 of 30

Using trig ratios to find side lengths

9-10Mathematics

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Learning Objective

Students will explore using trig ratios to find side lengths through guided practice and application.

Today's Lesson

This lesson focuses on using trig ratios to find side lengths. Mathematics provides tools for modeling and analyzing complex systems.

A ratio compares two quantities. For example, if there are 3 boys and 5 girls in a group, the ratio of boys to girls is 3:5 (read "3 to 5"). Ratios can also be written as fractions (3/5) or with the word "to" (3 to 5). Ratios help us compare amounts and understand relationships between numbers in recipes, maps, and many real-world situations.

As you engage with this material, consider both the theoretical foundations and practical applications. Think critically about how this concept builds on prior knowledge and where you might apply it beyond the classroom.

Challenge yourself to go beyond memorization—seek to understand the "why" behind the processes and principles.

Key Terms
Problem

A mathematical question requiring analysis and solution

Solution

The result obtained by solving a problem

Activities
Instructions
1. Review the example problems for using trig ratios to find side lengths. 2. Identify the steps and strategies used. 3. Work through practice problems independently. 4. Compare solutions with a partner.
Materials Needed
  • Notebook
  • Calculator (if needed)
  • Graph paper
Practice Problems
1

The ratio of boys to girls is 3:5. If there are 6 boys, how many girls are there?

Hint: Set up a proportion: 3/5 = 6/x
2

Express the ratio 6:9 in simplest form.

Hint: Divide both numbers by their GCF.
3

If 4 apples cost $2, how much do 10 apples cost?

Hint: Set up a proportion or find unit price.

Teaching Tip

For advanced learners: Encourage deeper analysis and real-world connections. Consider extension activities that allow students to apply using trig ratios to find side lengths to novel situations.

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