Algebra I / Elem. Algebra
Introduction to Algebra Linear Equations and Inequalities Functions and Graphs I Lines and thier Graphs Linear Systems
Algebra II / E&I Algebra
Exponents & Polynomials Intermediate Algebra starts here!

Factoring Rational Expressions Rational Equations and Applications
Algebra III / Inter. Algebra
Radical Expressions Nonlinear Equations and Applications Functions and Graphs II Exponential and Logarithmic Functions
College Algebra
Equations and Inequalitites Functions and Graphs Polynomial and Rational Functions Exponential and Logarithmic Functions Systems and Matrices Geometry Basics Conic Sections Sequences and Series
Trigonometry
The Six Trigonometric Functions Right Triangle Trigonometry Circular Functions Graphs of Trigonometric Functions Trigonometric Identities Trigonometric Equations Oblique Triangles and the Laws Vectors Complex, Parametric, and Polar Forms
Calculus I
Limits and Continuity Derivatives Analysis of Curves Antiderivatives
Calculus II
Transcendental Functions
Geometry Physics Integration Techniques Calculus of Infinity Parametric, Polar, and Conic Curves
Calculus III
Calculus IV
15.Functions of Several Variables
16.Multiple Integration
17.Vector Analysis

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:

• 7.3.1 Know the law of cosines formula
• 7.3.2 Understand that the law of cosines can be used in cases when the information given is of the form SAS or SSS
• 7.3.3 Solve oblique triangles using the law of cosines

Terminology

Define: included angle, law of cosines

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