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Calculus IV
15.Functions of Several Variables
16.Multiple Integration
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Course: Trigonometry
Topic: Oblique Triangles and the Laws
Subtopic: Law of Cosines

Overview

Continuing our study of oblique (non-right) triangles, in today's lesson we study the second of the two laws used to solve triangles, the law of cosines. It is used when two sides and the included angle be given, enabling us to find the third side, or three sides be given, enabling us to find an angle. In either case the law of sines is then used to complete the triangle.

Objectives

By the end of this topic you should know and be prepared to be tested on:

Terminology

Define: included angle, law of cosines

Memorize the Law of Cosines!
All three forms are shown below using standard triangle notation.