LESSON NOTES MENU
Calculus IV
15.Functions of Several Variables
16.Multiple Integration
17.Vector Analysis
S = contains supplemental resources
Course: Calculus III
Topic: Vectors and Geometry of Space
Subtopic: Cross Product

Overview

A cross product is one method of multiplying two 3D vectors. The operation is written with a cross (×) between the vectors such as <1,2,3>×<4,5,6>. While the answer to a dot product is a constant, the answer to a cross product is a vector, thus it is also known as a vector product. The answer vector is perpendicular to the plane spanned by the two original vectors. The orientation of the answer vector (ie. pointing up or down from the plane) is determined by the right hand rule. The cross product is used in vector analysis in a variety of STEM applications.

Objectives

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

Terminology

Define: cross product, vector product, norm, normal vector, determinant, adjunct, triple scalar product, parallelepiped, torque

Formulae to have in your notes:

Supplemental Resources (recommended)

Can your calculator perform Determinants, Dot Products, and Cross Products? See Prof. Keely's Calculator Guide: Determinants and Calculator Guide: Dot & Cross Products for steps on the Ti-84/86, TI-89, and HP-48.

CalcPlot3D is a nice little *free* interactive colour 3D graphing software (Java-based) worth checking out if you need one. More at CalcPlot3D Info. (Note that MAC computers already have a built-in 2D/3D grapher.)

Explore the geometric interpretation of cross product via one of the following interactive sites:

  1. Explore CalcPlot3D's Cross Product Exploration (Java-based).
  2. Go to Math Insight's Cross Product article. It's a pretty good read all around but in particular scroll down and play with the GeoGebra applet.
  3. Play with the Wolfram Demonstrations Project: Cross Product of Vectors.

Supplemental Resources (optional)

Better Explained's article Cross Product

Paul's OL Notes - Calc II: Cross Product

Patrick JMT Just Math Tutorials:
Cross Product and Torque: An Application of Cross Product

James Sousa's MathIsPower4U - Calc II:
Vector Cross Products
Find the Cross Product of Two Vectors
Find Two Unit Vectors Orthogonal to Two Given Vectors
Ex 1: Properties of Cross Products - Cross Product of a Sum and Difference
Ex 2: Properties of Cross Products - Cross Product of a Sum and Difference
Find the Area of a Triangle Using Vectors
Find the Distance Between Two Points In Space
An Application of Cross Products: Torque
The Triple Scalar Product: Volume of a Parallelepiped