Lesson 5

Lesson 5: Proving Trigonometric Identities

Focus

When a person decides to buy a vehicle, or a mechanic needs to fix a vehicle, that person will often reference the technical specifications for that vehicle. Specifications give details of things like vehicle size, parts, cost, and performance. But before the specifications are written, the car must go through a design process. Engineers spend a lot of time and thought trying to make the car appealing and functional.

An identity is like the specifications of a vehicle. An identity is a ready tool that a user can expect to give reliable information without a lot of thought. Just like a car must be designed before the specifics can be used, an identity must be proven before the identiry is used; the identity must go through a testing procedure to show it will always work properly. This testing procedure is called a proof.

Lesson Outcome

At the end of this lesson you will be able to prove a trigonometric identity.

Lesson Questions

In this lesson you will investigate the following questions:

• How can a trigonometric identity be proven?
• Why is it necessary to prove an identity?

Assessment

Your assessment may be based on a combination of the following tasks:

• completion of the Lesson 5 Assignment (Download the Lesson 5 Assignment and save it in your course folder now.)
• course folder submissions from Try This and Share activities
• additions to Glossary Terms
• work under Project Connection