Lesson 3 - Using trigonometry to find missing side lengths

Lesson overview

In this lesson you will:

Using trigonometry to find missing side lengths

Duration 1:02

During this lesson you will learn how to use the SOH, CAH and TOA equations to find missing side lengths in right-angled triangles.

In doing so, you will need to use techniques learnt when solving equations, for example inverse operations.

Watch the video, Trigonometry: Finding missing sides, to learn how to identify and use the correct equation (SOH, CAH or TOA) to find the missing side length.
If after watching the video, you’re not feeling confident in solving equations, visit the SOHCAHTOA page on the Third Space Learning website for more help with calculating the missing side lengths.

Trigonometry: Finding missing sides

Duration 7:54

Click on the image to open the Trigonometry interactive in a new tab.
Level 4 will give you more sine questions, or try Levels 2 and 5 for cosine and Levels 3 and 6 for tangent.

For the following right-angled triangles, label each side as opposite, adjacent or hypotenuse, determine which equation to use and then solve for x.

Complete the questions in your exercise book or folder, remembering to show all your working.

Finding the missing side activity

Don't forget to hand in the work you completed today!

Your teacher will have told you to do one of the following:
- Upload any digital documents you created and any photos you took of your written work to your Learning Management system (MS Teams, Google Classroom for example).
- Email any digital documents you created and any photos you took of your written work to your teacher.

Make sure you keep any hand written work you did in your exercise book or folder as your teacher may need to see these when you are back in class.

Let us know how you feel about this lesson.

Page updated

Report abuse