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:
- 7.2.1 Know the law of cosines formula
- 7.2.2 Understand that the law of cosines can be used in cases when the information given is of the form SAS or SSS
- 7.2.3 Solve oblique triangles using the law of cosines
Terminology
Define: included angle, law of cosines