Ch 15: Triangle Trigonometry

About This Chapter

Take a closer look at these lessons to gain insight about the steps needed for performing triangle trigonometry. Prepare for a test, improve your grades, or just use this chapter as supplemental information for your current trigonometry class.

Triangle Trigonometry - Chapter Summary

Early mathematicians studied the relationships among the angles and the sides of triangles, and by doing so developed the laws and theorems of trigonometry that we use for solving advanced equations. These lessons about triangle trigonometry give you a deeper understanding of the most essential theorems, formulas, and concepts needed for solving sample trigonometric equations.

While this chapter does address a significant amount of information, our instructors have found ways to make everything easier to understand. For starters, each chapter has been split into miniaturized lessons, so instead of scrolling through a seemingly endless chapter, you can pick the individual lesson topics you want to go over. We also keep each lesson brief, making sure you remain focused on the most essential information. By completing this chapter, you will be able to do the following:

  • Describe trigonometric similarity and ratios
  • Identify how to find trigonometric ratios
  • Analyze the cosine and sine of complementary angles
  • Point out steps for solving right triangle sample problems
  • Review the use and applications of the Pythagorean Theorem
  • Show how to use the Pythagorean Theorem for finding distances
  • Determine how the Pythagorean Theorem applies to trigonometry
  • Establish finding the area of a triangle using sine
  • Apply the law of cosines and the law of sines to practice problems

6 Lessons in Chapter 15: Triangle Trigonometry
Test your knowledge with a 30-question chapter practice test
Trigonometric Ratios and Similarity

1. Trigonometric Ratios and Similarity

Where do terms like sine, cosine and tangent come from? In this lesson, we'll learn about how similarity with right triangles leads to trigonometric ratios.

Practice Finding the Trigonometric Ratios

2. Practice Finding the Trigonometric Ratios

So you know what sine, cosine and tangent are. Great! But how do you use them? Find out how in this lesson as we find missing sides and angles using trigonometric ratios.

The Pythagorean Theorem: Practice and Application

3. The Pythagorean Theorem: Practice and Application

The Pythagorean theorem is one of the most famous geometric theorems. Written by the Greek mathematician Pythagoras, this theorem makes it possible to find a missing side length of a right triangle. Learn more about the famous theorem here and test your understanding with a quiz.

Calculating Angles for a 5-12-13 Triangle

4. Calculating Angles for a 5-12-13 Triangle

How do you calculate the angles of a triangle when you only know the lengths of the sides? This lesson will go over a step-by-step process to calculate the angles, using a triangle whose sides are 5, 12 and 13 units long.

Finding Distance with the Pythagorean Theorem

5. Finding Distance with the Pythagorean Theorem

How much faster is it to cut the corners in a race around the block? In this lesson, review the Pythagorean Theorem, and figure out how to solve without a right triangle.

Trigonometry and the Pythagorean Theorem

6. Trigonometry and the Pythagorean Theorem

Explore how the Pythagorean Theorem can be used in conjunction with trigonometric functions. In this lesson, take an inverse trigonometric function, and define all three sides of a right triangle.

Chapter Practice Exam
Test your knowledge of this chapter with a 30 question practice chapter exam.
Not Taken
Practice Final Exam
Test your knowledge of the entire course with a 50 question practice final exam.
Not Taken

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.