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Alignment
- Standards Alignment
- Textbook Alignment
Subject Area
- Math: Precalculus: Trigonometry (Triangle and Circular Functions)
Author

Texas Instruments
Level

9-12
Activity Time

20 Minutes
Device
- TI-Nspire™ Navigator™
- TI-Nspire™
- TI-Nspire™ CAS
Software

TI-Nspire™
TI-Nspire™ CAS
TI-Nspire Version

2.0
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What's the Difference?

Published on 08/12/2010

The angle difference formula for cosine is explored.

Students begin by exploring a geometric representation of angle difference as they review unit circle concepts.
The angle difference formula for cosine is applied to angles other than those often committed to memory through use of the unit circle. Students test their accuracy through the manipulation of a unit circle with a moveable point and displayed coordinates.
An optional extension for students is the derivation of the angle difference and sum formulas for cosine. Diagrams similar from Problem 1 are used along with the Law of Cosines and the distance formula to obtain these two useful trigonometric identities.