Law of Cosines

Author

Texas Instruments

Alignment

Standards Alignment

Textbook Alignment

Subject Area

Math: Precalculus: Trigonometric Laws and Identities

Level

9-12

Activity Time

45 Minutes

TI Calculator

TI-Nspire™ CX/CX II

TI-Nspire™ CX CAS/CX II CAS

TI-Nspire™

TI-Nspire™ CAS

TI-Nspire Version

3.2

Resource Types

Lessons

Format

TNS

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Law of Cosines

Activity Overview

This lesson involves visualizing and exploring the Law of Cosines.

Objectives

Students will be able to state the Law of Cosines.
Students will be able to apply the Law of Cosines to find missing sides and angles in a triangle.
Students will understand why the Law of Cosines is true.

Vocabulary

cosine of an angle
obtuse angle
acute angle
right angle

About the Lesson

This lesson involves visualizing and exploring the Law of Cosines.
As a result, students will:

Manipulate a triangle to observe the equality of the Law of Cosines.
Manipulate a triangle to discover why the Law of Cosines is true.
Consider the Law of Cosines in connection with previous knowledge about right triangle trigonometry.
Determine when the Law of Cosines can be used to solve for unknown side lengths and angle measures in a triangle, and apply it to solve when possible.

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Lesson Files

Teacher Notes PDF Student Activity DOC Student Activity PDF TI-Nspire Activity TNS

Author

Texas Instruments

Alignment

Standards Alignment

Textbook Alignment

Subject Area

Math: Precalculus: Trigonometric Laws and Identities

Level

9-12

Activity Time

45 Minutes

TI Calculator

TI-Nspire™ CX/CX II

TI-Nspire™ CX CAS/CX II CAS

TI-Nspire™

TI-Nspire™ CAS

TI-Nspire Version

3.2

Resource Types

Lessons

Format

TNS

Report an Issue

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Law of Cosines

Law of Cosines

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